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Turtle and Dugong Monitoring Post-dredging Report

Ichthys Nearshore Environmental Monitoring Program L384-AW-REP-10250

3.6 and Grid 16 = 5.81

Prepared for INPEX March 2015

Turtle and Dugong Monitoring Post-dredging Report

Ichthys Nearshore Environmental Monitoring Program L384-AW-REP-10250

Turtle and Dugong Monitoring Post-dredging Report Ichthys Nearshore Environmental Monitoring Program

Document Information Prepared for INPEX Project Name Ichthys Nearshore Environmental Monitoring Program File Reference L384-AW-REP-10250_0_Turtle and Dugong Post-dredging Report.docm Job Reference L384-AW-REP-10250 Date March 2015

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Document Control Version Date Author Author

Initials Reviewer Reviewer

Initials

A 22/01/2015 Ivon Sebastian Freya Muller Andrea Nicastro

IS FM AN

Dr Craig Blount Dr Michelle Blewitt Dr Lachlan Barnes

CB MLB LB

B 09/03/2015 Freya Muller FM Dr Craig Blount CB

0 26/03/2015 Freya Muller FM Dr Craig Blount CB

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Executive Summary The Turtle and Dugong Monitoring Program (TDMP) was developed to monitor for potential impacts to the distribution and abundance of turtles and dugongs around Darwin Harbour and surrounding inshore waters during dredging and spoil disposal activities associated with the Ichthys LNG Project (the Project). The monitoring program used aerial surveys at three locations (referred to as blocks), Impact block (IM; Darwin Harbour/Hope Inlet region where Project dredging activities occurred) and at two Control blocks, Control block 1 (C1; Bynoe Harbour) and Control block 2 (C2; around the Vernon Islands, across to Melville Island). In addition, finer-scale surveys were undertaken during the Baseline Phase via boat surveys and via land-based surveys during the Dredging and Post-dredging Phase, which gave insight into the movements and distribution of turtles and dugongs within Darwin Harbour and the surrounding areas. Satellite tagging of four juvenile green turtles (in the IM block) and one adult hawksbill turtle provided further information at a finer-scale about behaviour, movements and habitat utilisation of these species of turtles.

Monitoring for the TDMP was carried out during the Baseline Phase, prior to the commencement of dredging activities in 2012 (B1: May 2012, B2: July 2012 and B3: October 2012), and the Dredging Phase, which included surveys following Season One East Arm (EA) dredging operations during the 2013 dry season dredging hiatus (D2: May 2013, D3: July 2013, D4: October 2013) and during Gas Export Pipeline (GEP) dredging operations and Season Two EA dredging during the 2014 dry season (D5: May 2014). Post-dredging Phase surveys (P1: July 2014, P2: October 2014) were undertaken following the completion of Season Two EA dredging operations on 11 June 2014 and GEP dredging on 12 July 2014. Data collected following the completion of dredging operations (Post-dredging Phase) were compared with those collected prior to (Baseline Phase) and during dredging activities (Dredging Phase). This Post-dredging report provides a description and interpretation of results of Post-dredging Phase surveys P1 and P2 and a summary of all Baseline and Dredging Phase results collected as part of the TDMP. However, due to poor weather conditions during the P1 survey, only results based on raw sightings are presented for P1.

Raw sightings of dugongs and subsequently estimates of abundance based on these sightings have been variable throughout the TDMP. Although no obvious trends in dugong numbers were identified, results suggest that abundance fluctuates naturally about the mean for all three blocks (C1, C2 and IM). During the Post-dredging Phase, the relative abundance of dugongs (as estimated using the Marsh and Sinclair (1989) method) ranged from 123 ± 59 in C1 to 306 ± 188 in IM, which is consistent with aerial survey data collected in the Baseline and Dredging Phases. Estimates calculated using the Pollock et al. (2006) method were lower than those obtained from the Marsh and Sinclair (1989) method during the Post-dredging Phase (ranging from 61 ± 20 in C1 to 187 ± 104 in IM), as has been observed throughout the TDMP. Generally, dugong sightings over the duration of the monitoring program were comparably higher within the IM block compared to the Control blocks, with the exception of during D5 (May 2014), where C2 had the greatest mean number of sightings (321 ± 172) and during D2 (May 2013), where sightings were similar between C2 and IM blocks (93 ± 45; 99 ± 48 respectively).

During the Post-dredging Phase, and throughout the TDMP, there was a higher frequency of dugong sightings in shallow areas (0 m to -10 m Lowest Astronomical Tide; LAT) within all three blocks, with most dugongs sighted between East Point and Lee Point in Darwin Outer. Few dugongs were sighted in Darwin Harbour Inner, with sightings generally recorded around the Weed Reef area. The observed variability in dugong sightings between replicate flights and among surveys, along with spatial patterns in abundance within the three blocks, is likely a result of a number of factors including seasonal variation in the distribution and density of seagrass which is the primary food source for dugongs, resulting in the temporary movement of dugongs in search of optimum foraging areas. Overall, there has been no evidence to suggest Project related impacts on dugong abundances and their distribution throughout the TDMP.

Numerous turtles were sighted throughout the monitoring program and although aerial observers could not identify individual turtles to species level, sightings were likely to be green, hawksbill, olive ridley or flatback turtles, all of which have been previously recorded in Darwin Harbour. Sightings were widespread within each block and overall sightings were relatively high in comparison to dugongs. Like dugongs, turtle abundances seemed to fluctuate naturally about a mean and although temporal and spatial variations were evident, no trends were detected. During the Post-dredging Phase, the estimated abundance of turtles

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(based on the Marsh and Sinclair (1989) method) ranged between 626 ± 194 at C1 and 684 ± 160 at C2, which was consistent with aerial survey data collected in the Baseline and Dredging Phases. However, abundances in Post-dredging Phase based on the Pollock et al. (2006) method increased substantially from Baseline and Dredging Phase estimates, ranging from 1,235 ± 258 in C2 to 1,332 ± 412 in IM. During P2, mean turtle numbers in the IM block (based on raw sightings) were similar to the Control blocks (C1 and C2). However, across a majority of all other surveys during the Baseline and Dredging Phases, mean turtle sightings in the IM block were generally lower when compared to Control blocks.

It is not clear why fewer turtles were sighted in the IM block during the Baseline and Dredging Phases compared to the Post-dredging Phase, although as this result has been observed consistently between those two Phases it does not indicate an effect of Project activities. It is worth noting that in the final Post-dredging Phase survey (P2), raw sightings and population estimates of turtles (based on both estimation methods) were similar for the three blocks and generally amongst the highest recorded for the entire TDMP. These findings indicate that no effects of Project activities on turtle abundance have been detected by the TDMP in the Darwin region. It is considered that the observed temporal variability in turtle sightings among surveys and smaller-scale spatial variability within the survey blocks were likely a result of seasonal movements and habitat preferences of the various turtle species that occur in the Darwin region.

Land-based surveys provided fine-scale information on green turtles present and their distribution at Channel Island Bridge. While tagging and satellite tracking of turtles provided additional information on habitat usage and potential foraging areas of juvenile green turtles at Channel Island. Juvenile green turtles tagged at Channel Island remained within smaller core home ranges in shallow waters close to the tagging location. The depth profiles of these tagged turtles likely reflect dietary preferences, such as shallow water marine plants for the juvenile green turtles. A hawksbill turtle released at Nightcliff Jetty (opportunistically tagged following rehabilitation after being rescued by from an illegal fishing vessel by Australian Fisheries Management Authority (AFMA)) also appeared to exhibit a core range, remaining in deeper water about 30 km from the shore. This is likely a reflection of the distribution of deep water sponges which are the dietary preference for hawksbill turtles.

In summary, while spatial and temporal variations have been observed in the distribution and abundance of turtles and dugongs over the duration of the TDMP, on the balance of available evidence, these differences appear most likely due to natural variation. As such, there appears to be no indication that Project dredging activities have affected turtle or dugong distribution or population sizes in the Darwin region.

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Glossary

Term or Acronym Definition

Availability bias A bias in the data affected by an animal being concealed by an environmental factor so that is not visible to the observer

ACF Availability Correction Factor

B1 Baseline survey 1: 1 June 2012 to 8 June 2012 (2 replicate flights)

B2 Baseline survey 2: 18 July 2012 to 5 August 2012 (3 replicate flights)

B3 Baseline survey 3: 29 September 2012 to 21 October 2012 (3 replicate flights)

BHD Backhoe Dredger

BSS Beaufort Sea State is an empirical measure (0 to 12) for the intensity of the wind based mainly on sea state or wave conditions, with 0 refering to calm, mirror like seas and 12 refers to hurricane conditions

C1 Control block 1 (Bynoe Harbour)

C2 Control block 2 (Vernon Islands to Melville Island)

CITES Convention on International Trade of Endangered Species

CSD Cutter Suction Dredger

CV Coefficient of Variation is used to compare the standard deviations between populations with different means and it provides a measure of variation that is independent of the measurement units

D1 Completed during Backhoe Dredger (BHD) operations only where impacts are considered minimal and thus D1 survey is referred to as Baseline survey 3 (B3)

D2 Dredging survey 2: 11 May 2013 to 23 May 2013 (2 to 3 replicate flights)

D3 Dredging survey 3: 27 July 2013 to 10 August 2013 (3 replicate flights)

D4 Dredging survey 4: 13 October 2013 to 27 October 2013 (3 replicate flights)

D5 End of Dredging survey 5: 10 May 2014 to 24 May 2014 (2 to 3 replicate flights)

Darwin Harbour Inner

Representing Darwin Harbour waters closest to dredging activities, within a seaward demarcation boundary extending approximately northeast across the harbour mouth from Mandorah to East Point, including Woods Inlet and Fannie Bay.

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Darwin Outer

Representing waters within the harbour and those more remote from dredging, beyond the seaward demarcation boundary of Darwin Harbour Inner and including areas that are in proximity to the spoil disposal ground (e.g. Charles Point, Shoal Bay and Gunn Point)

DLRM Department of Land Resource Management

Double platform

A sampling method using two observers to sample a given species in the same area at the same time. The two observers must be independent of each other and isolated visually and acoustically. On aerial surveys, the two observers are normally arranged as a front and rear observer

DSDMP Dredging and Spoil Disposal Management Plan

EA East Arm

EPBC Act Environment Protection and Biodiversity Conservation Act 1999

GEP Gas export pipeline

GIS Geographic Information System

Group size Mean group size of a group of dugongs or turtles observed during aerial surveys

IM Impact block (Darwin Harbour/Hope Inlet to Gunn Point)

LC Location Class

n Sample size

NEMP Nearshore Environmental Monitoring Plan

P1 Post-dredging survey 1: 8 July 2014 to 20 July 2014 (3 replicate flights)

P2 Post-dredging survey 2: 11 October 2014 to 20 October 2014 (3 replicate flights)

PB Port observers – both front and rear

PCF Perception Correction Factor

Perception bias A bias in the data caused by an observer not seeing an animal despite it being visible

PERMANOVA Permutational Analysis of Variance

PF Port observer – front only

Population estimate An estimate of the number of individual animals living in one place at the one time

p-perm Equivalent to the traditional p-value but derived from permutational analyses (PERMANOVA)

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PR Port observer – rear only

QA/QC Quality Assurance/Quality Control

Recapture The event of one individual or group of animals being counted (and thus recorded) a subsequent time by the rear observer during aerial surveys

SB Starboard observers – both front and rear

SE Standard error of the mean

SF Starboard observer – front only

SR Starboard observer – rear only

TDMP Turtle and Dugong Monitoring Program

Turbidity Turbidity is an indication of water clarity

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Table of Contents Executive Summary iii Glossary v

1 Introduction 1 1.1 Overview 1 1.2 Background 1 1.3 Summary of Baseline Phase Sampling Results 1 1.4 Summary of Dredging Phase Sampling Results 2 1.5 Objectives 3

2 Methodology 4 2.1 Field Monitoring Schedule 4 2.2 Field Sampling Locations 6

2.2.1 Aerial Surveys 6 2.2.2 Land-based Surveys 6 2.2.3 Turtle Tagging 6

2.3 Field Methods 9 2.3.1 Monitoring Permits 9 2.3.2 Aerial Surveys 9 2.3.3 Land-based Surveys 10

2.4 Assumptions and Constraints 11 2.4.1 Aerial Surveys 11 2.4.2 Land-based Surveys 11 2.4.3 Turtle Tagging 12

2.5 Data Analysis 12 2.5.1 Aerial Surveys 12 2.5.2 Land-based Surveys 15 2.5.3 Turtle Tagging 15

2.6 Quality Assurance/Quality Control (QA/QC) 15 3 Dredging Operations 17

4 Results 19 4.1 Aerial Surveys 19

4.1.1 Survey Effort and Environmental Conditions 19 4.1.2 Dugongs 20 4.1.3 Turtles 38

4.2 Land-based Surveys 59 4.2.1 Survey Effort and Environmental Conditions 59 4.2.2 Channel Island Bridge 59 4.2.3 Cullen Bay Rock Wall 59

4.3 QA/QC for Aerial and Land-based Surveys 62 4.4 Rehabilitated Turtles 62

5 Discussion 65 5.1 Dugongs 65 5.2 Turtles 66

6 Conclusion 67

7 Acknowledgements 68

8 References 69

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Tables

Table 2-1 Monitoring schedule for the TDMP 5 Table 3-1 Dredge footprint summary 17 Table 4-1 Details of group size estimates and correction factors used in dugong population estimates for

P2 (October 2014) aerial surveys 30 Table 4-2 Sighting histories for dugong groups sighted during P2 aerial surveys by individual observers for

all flights combined* 30 Table 4-3 Comparison of dugong population estimates (±SE) and number of replicates where estimates

were able to be derived (n) for: a) each block during B3, D4 and P2; and b) across Baseline, Dredging and Post-dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006) 32

Table 4-4 Results of univariate PERMANOVA tests for differences in the density of dugongs per km2 based on: a) the Marsh and Sinclair (1989) method; b) the Pollock et al. (2006) method; and c) raw sightings between three Phases (Baseline, Dredging and Post Dredging), including Phase (B1, B2 and B3 within Baseline Phase; D2, D3, D4 and D5 within Dredging Phase; and P1 and P2 within the Post-dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) 37

Table 4-5 Details of turtle group size estimates for whole blocks and correction factors used in population estimates for the P2 aerial surveys 48

Table 4-6 Sighting histories for turtles sighted during P2 aerial surveys by individual observers for each replicate flight, and all flights combined* 48

Table 4-7 Comparison of turtle population estimates (±SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B3 (October 2012), D4 (October 2013) and P2 (October 2014); and b) across the Baseline, Dredging and Post-dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006) 50

Table 4-8 Results of univariate PERMANOVA tests for differences in the density of turtles per km2 based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings between three Phases (Baseline, Dredging and Post Dredging), including Phase (B1, B2 and B3 within Baseline Phase; D2, D3, D4 and D5 within Dredging Phase; and P1 and P2 within the Post Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) 54

Table 4-9 Turtle population estimates (±SE) for each sub-block during P2 (October 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006), averaged across replicate flights 56

Table 4-10 Turtle density estimates (per km2) for each sub-block during P2 (October 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006) 57

Table 4-11 Survey effort for land-based surveys during P2 (October 2014) 59 Table 4-12 Number of megafauna sightings and number of individual animals observed at Channel Island

Bridge and Cullen Bay rock wall during P2 (October 2014) land-based surveys 60 Table 4-13 Total number of megafauna sightings observed at Channel Island Bridge and Cullen Bay rock

wall during all Dredging (D2, D3, D4 and D5) and Post-dredging Phase (P2) land-based surveys N.B. Counts are of total sightings, not individuals. Land-based surveys were not undertaken during the Baseline Phase (2012) or during P1 (July 2014) 60

Figures Aerial survey blocks and sub-divisions encompassing Bynoe Harbour (C1), Darwin Figure 2-1

Harbour/Hope Inlet region (IM) and Vernon Islands (C2) 7 Land survey sites in Darwin Harbour during P2 (October 2014); Cullen Bay rock wall (left); and Figure 2-2

Channel Island Bridge (right), also showing the turtle tagging site 8 Plane window calibration for aerial surveys (top dotted line = upper limit of Very High zone; Figure 2-3

bottom dotted line = lower limit of Low zone) 10

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Aerial survey density grid cells for Darwin Harbour/Hope Inlet area (IM) divided into Darwin Figure 2-4Harbour Inner and Darwin Outer regions 14

EA dredging footprint and GEP route 18 Figure 3-1 Distribution of dugongs (based on raw sightings) among and within sub-blocks during P2 aerial Figure 4-1

surveys (three replicate flights of C1, IM and C2) 22 Density of dugong sightings (based on raw counts) per km2 of transect area sampled over water Figure 4-2

within 6 km x 6 km grids at IM during P2 (October 2014) 23 Relative difference in dugong density (based on raw counts) per km2 of transect area sampled Figure 4-3

over water within 6 km x 6 km grids in IM during P2 (October 2014) compared with B3 (October 2012) 24

Relative difference in the dugong density (based on raw counts) per km2 of transect area Figure 4-4sampled over water within 6 km x 6 km grids at IM during P2 (October 2014) compared with D4 (October 2013) 25

Proportion of dugong sightings within different depth ranges (m) below LAT in: a) C1; b) IM; and Figure 4-5c) C2 for B1 (May 2012) to P2 (October 2014) surveys 27

Proportion of dugong sightings with respect to benthic habitat types at: a) C1; b) IM; and c) C2 Figure 4-6for B1 (May 2012) to P2 (October 2014) surveys 28

Mean population estimates and raw sighting numbers (±SE) for dugongs in each block during Figure 4-7the TDMP from B1 (May 2012) to P2 (October 2014), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings data 33

Mean dugong density per km2 (±SE) in each block during the TDMP from B1 (May 2012) to P2 Figure 4-8(October 2014), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings 35

Mean dugong population density estimates for all Phases combined calculated using the Marsh Figure 4-9and Sinclair (1989) method at Control and Impact treatments 36

Dugong population density, averaged over all blocks, using the Marsh and Sinclair (1989) Figure 4-10method 36

Distribution of turtles (based on raw sightings) during the P2 (October 2014) aerial survey 39 Figure 4-11 Density of turtle sightings (based on raw counts) per km2 of transect area sampled over water Figure 4-12within 6 km x 6 km grids in IM during the P2 (October 2014) aerial survey 40

Relative difference in turtle density (based on raw counts) per km2 of transect area sampled Figure 4-13over water within 6 km x 6 km grids in IM during the P2 (October 2014) aerial survey compared to B3 (October 2012) 41

Relative difference in the turtle density (based on raw counts) per km2 of transect area sampled Figure 4-14over water within 6 km x 6 km grids in IM during the P2 (October 2014) aerial survey compared to D4 (October 2013) 42

Proportion of turtle sightings observed within different depth ranges (m) below LAT in: a) C1; b) Figure 4-15IM; and c) C2 for B1 (May 2012) to P2 (October 2014) aerial surveys 44

Proportion of turtle sightings observed with respect to benthic habitat types at: a) C1; b) IM; and Figure 4-16c) C2 for B1 (May 2012) to P2 (October 2014) 45

Mean population estimates and raw sighting numbers (±SE) for turtles in each block during the Figure 4-17TDMP from B1 (May 2012) to P2 (October 2014), based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) population estimate methodologies; and c) raw sightings data 47

Mean turtle density per km2 (±SE) in each block during the TDMP from B1 (May 2012) to P2 Figure 4-18(October 2014), based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings data 52

Turtle population density calculated using the Marsh and Sinclair (1989) method at Control and Figure 4-19Impact treatments during Baseline, Dredging and Post-dredging Phases 55

Turtle population density calculated using the Pollock et al. (2006) method at Control (C1 and Figure 4-20C2) and Impact blocks (IM) across all surveys 55

Turtle population density calculated using raw sightings at Control (C1 and C2) and Impact Figure 4-21blocks (IM) 55

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Mean population estimates (±SE) for turtles derived from whole block and sub-block Figure 4-22calculations based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) at each block for P2 (October 2014) 58

Distribution of megafauna sighted during land-based surveys in P2 (October 2014) 61 Figure 4-23 Transmitted geo-locations of ‘Linh’, between 27 March 2014 and 16 August 2014 63 Figure 4-24 Proportion of dives at specific depths (m) for tagged rehabilitated turtle ‘Linh’ 64 Figure 4-25 Proportion of dives for specific durations (min) for tagged rehabilitated turtle ‘Linh’ 64 Figure 4-26

Appendices Appendix A Summary of Aerial Survey Effort during Baseline, Dredging and Post-dredging Phase

surveys Appendix B Summary of Dugong Sightings across Baseline, Dredging and Post-dredging Phase surveys Appendix C Summary of Dugong and Turtle Sightings overlaid with confirmed seagrass habitat during

B3, D4 and P2 surveys Appendix D Dugong Population Size Estimates during Baseline, Dredging and Post-dredging Phase

surveys Appendix E Corrected Dugong Densities during Baseline, Dredging and Post-dredging Phase surveys Appendix F Summary of Turtle Sightings across Baseline, Dredging and Post-dredging Phase surveys Appendix G Turtle Population Size Estimates during Baseline, Dredging and Post-dredging Phase

surveys Appendix H Corrected Turtle Densities during Baseline, Dredging and Post-dredging Phase surveys Appendix I Turtle Sub-block Population Size Estimates during P2 Aerial Surveys Appendix J Corrected Turtle Sub-block Densities during P2 Aerial Surveys Appendix K Land Survey Data during P2 Survey Appendix L Rehabilitated Turtle Summary Data

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1 Introduction

1.1 Overview INPEX is the operator of the Ichthys LNG Project (the Project). The Project comprises the development of offshore production facilities at the Ichthys Field in the Browse Basin, some 820 km west-south-west of Darwin and 450 km north-northeast of Broome, an 889 km long subsea gas export pipeline (GEP) and an onshore processing facility and product loading jetty at Bladin Point on Middle Arm Peninsula in Darwin Harbour. To support the nearshore infrastructure at Bladin Point, dredging works have been carried out to extend safe shipping access from near East Arm Wharf to the new product loading facilities at Bladin Point which are supported by piles driven into the sediment. A trench has also been dredged to seat and protect the GEP for the Darwin Harbour portion of its total length. Dredged material has been disposed at the spoil ground located approximately 12 km north-west of Lee Point. A detailed description of the dredging and spoil disposal methodology is provided in Section 2 of the East Arm (EA) Dredging and Spoil Disposal Management Plan (DSDMP) (INPEX 2013) and GEP DSDMP (INPEX 2014).

1.2 Background Following an Environmental Impact Assessment (INPEX 2011) the Project was approved subject to conditions that included monitoring for potential effects of dredging or spoil disposal on local ecosystems. Marine turtles and dugongs were included among the species to be monitored although the risk to populations within Darwin Harbour due to dredging and construction activities was considered minimal.

Dugongs are listed as ‘threatened with extinction’ under the Convention on International Trade of Endangered Species (CITES) and as ‘vulnerable to extinction’ in the International Union for the Conservation of Nature and Natural Resources Red Data Book of Threatened Species. In Australian waters, dugongs are listed as ‘migratory’ under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

Dugongs forage selectively on seagrass, their preferred diet, particularly tropical genera such as Halodule and Halophila (Preen 1992). Dugongs have also been sighted feeding on algal covered rocky reefs in the Darwin region (Whiting 2002). Calving occurs from late August to November and predominantly in protected shallow waters such as tidal sandbanks and estuaries (Marsh 1999), although the reproductive rate of individuals is inconsistent (Lanyon 2007). In the Northern Territory, areas of critical habitat for conservation have been declared under Section 37 of the Territory Parks and Wildlife Conservation Act 2001 but these are outside of the construction areas of the Project.

Of the six species of marine turtles known to be present in Australian waters, four are considered to occur around the Darwin region; these are green, hawksbill, olive ridley and flatback turtles. These species are listed as ‘threatened with extinction’ under CITES. In Australian waters, olive ridley turtles are listed as ‘endangered’, while green, hawksbill and flatback turtles are listed as ‘vulnerable’ under the EPBC Act.

All marine turtles have the same general life cycle. They grow slowly and take decades to reach sexual maturity. Between 20 and 50 years, males and females leave their feeding grounds and migrate up to 3,000 km to a nesting area located in the region of their birth. Green turtles (immature and adult) have been observed in both reef and non-reef habitats around the Darwin region (Whiting 2000). Within Darwin Harbour, green and hawksbill turtles are occasionally sighted near Channel Island, with green turtles also sighted near Weed Reef (Whiting 2000). Olive ridley turtles are rarely sighted in shallow waters and are known to occur only occasionally in Darwin Harbour (NAILSMA 2006). Flatback turtle is the most commonly encountered nesting species in Darwin Harbour during the dry season (Chatto and Baker 2008). Casuarina Beach, a popular Darwin beach, has been monitored for nesting turtles since the mid-1990s (Chatto and Baker 2008).

1.3 Summary of Baseline Phase Sampling Results Baseline Phase aerial surveys (B1: May 2012, B2: July 2012, B3: October 2012) for the TDMP were carried out in an area encompassing Darwin Harbour/Hope Inlet to Gunn Point (Impact location – IM) and at two Control locations (Control location 1, to the west of IM – C1; and Control location 2, to the east of IM – C2),

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prior to the commencement of Cutter Suction Dredger (CSD) operations in East Arm (4 November 2012). Baseline survey 3 (B3) was originally termed Dredging survey 1 (D1) and undertaken after the commencement of the Backhoe Dredger (BHD) operations on 27 August 2012. However, given this was prior to the start of the CSD operations and considering the likely minimal impacts of BHD, D1 was renamed B3. This reallocation of the survey into the Baseline Phase was further supported by statistical analyses comparing B1, B2 and B3, which found no statistical difference in abundance of dugongs (or turtles) between the three Baseline Phase surveys.

During the Baseline Phase, a total of 263 dugongs and 1,903 turtles were sighted. The average size of the dugong population in C1 was estimated to be 176 ± 67 dugongs during B1, 287 ± 65 dugongs during B2 and 157 ± 118 dugongs during B3 (using Marsh and Sinclair (1989) method). Estimates of population size made for C2 were similar to those made for C1. The highest population estimates were associated with the IM block, with 243 ± 67 dugongs during B1, 411 ± 139 dugongs during B2 and 401 ± 185 dugongs during B3. Spatial and temporal estimates of dugong density, based on calculations of corrected data, followed closely the patterns obtained for population size. In C1, densities ranged from 0.34 dugongs/km2 in B2 to 0.19 dugongs/km2 in B3, with estimates for C2 similar. The greatest densities of dugongs were observed in the IM block during B3, at 0.35 dugongs/km2.

The total number of turtles sighted during B3 (n = 984) was considerably higher than for B1 (n = 334) and B2 (n = 585). Population size estimates for turtles varied among surveys and locations, though not significantly among surveys. In C1, Baseline Phase population estimates were 335 ± 47 turtles during B1, 1,333 ± 213 turtles during B2, and 778 ± 174 turtles in B3, with similar results for C2. Comparable to dugongs, population sizes of turtles were greatest in the IM block, with 739 ± 188 turtles in B1, 1,469 ± 369 turtles in B2, 868 ± 124 turtles in B3. The full Baseline Phase results of the TDMP are reported in the Turtle and Dugong Monitoring Program Baseline Report (Cardno 2013a) and Dredging Report 1 (Cardno 2013b).

1.4 Summary of Dredging Phase Sampling Results Monitoring during the Dredging Phase included aerial and land-based surveys following Season One dredging operations during the 2013 dry season dredging hiatus (D2: May 2013, D3: July 2013, D4: October 2013) and during GEP and Season Two EA dredging operations in the 2014 dry season (D5: May 2014). Land-based surveys were also completed at two ‘hotspots’ within IM (Channel Island Bridge and Cullen Bay Rock Wall).

During the Dredging Phase, a total of 288 dugongs and 699 turtles were sighted in aerial surveys. An additional 46 dugongs and 634 turtles were sighted in land-based surveys; although it is noted that some of these were likely to have been resightings of the same individuals.

The average population sizes (as estimated using the Marsh and Sinclair (1989) method) of dugongs for all blocks across the Dredging Phase were estimated to be 305 ± 173 at IM, 165 ± 63 at C1 and 251 ± 172 at C2. The highest population estimates for dugongs during the Dredging Phase were observed in the IM block where the average size of populations were estimated to be 99 ± 48 during D2, 315 ± 170 during D3, 382 ± 154 during D4 and 280 ± 79 during D5. The average estimate of dugong populations in C1 throughout the Dredging Phase was 134 ± 58 during D3, 181 ± 84 during D4 and 173 ± 54 during D5. Estimates for C2 block were generally higher than C1 with 93 ± 45 during D2, 260 ± 121 during D4 and 321 ± 172 during D5. Due to low sightings (≤ 5 individuals) in C1 and C2 during D2 and D3 respectively, population estimates in these blocks (and subsequent densities per km2) were unable to be calculated for these surveys. Dugong population estimates based on the Pollock et al. (2006) method were generally lower across all blocks throughout the Dredging Phase.

Similar patterns were evident in the spatial differences for dugong density (as derived from Marsh and Sinclair (1989) population estimates), with the highest mean densities for the Dredging Phase recorded within IM block. There was significant variability in dugong densities between surveys throughout the Dredging Phase, although there was no evidence of a temporal trend. Densities across all blocks (IM, C1 and C2) were lowest during D2. For IM, densities showed an overall increase from D2 to D4 (0.09/km2 and 0.37/km2 respectively, based on Marsh and Sinclair (1989)), followed by a slight decrease in D5 (0.27/km2). For C1, dugong densities were more consistent throughout the Dredging Phase (D3 = 0.2/km2, D4 = 0.26/km2, D5 = 0.25/km2), while densities in C2, appeared to increase slightly (D2 = 0.09/km2, D4 = 0.27/km2, D5 = 0.33/km2). During the Dredging Phase, dugong densities in the IM block were greatest within



the Darwin Outer region, between East Point and Lee Point, with few dugongs sighted with Darwin Harbour Inner.

The total number of turtles sighted during aerial surveys in the Dredging Phase was 2,796, with an average of 699 ± 73 turtles per survey. The highest mean number of turtles were sighted during D5 (151 ± 15), while the lowest mean was observed during D3 (65 ± 12). Over the Dredging Phase, population estimates for turtles (based on the Marsh and Sinclair (1989) method) were similar, with means of 677 ± 205 in C1 and 538 ± 173 in IM. Mean population estimates for C2 were the highest across the Dredging Phase at 745 ± 243.

Differences in densities of turtles between Dredging Phase surveys were small. Across all replicate flights in C1 (n = 12) during the Dredging Phase, the average turtle density based on raw sightings was 0.58/km2 ± 0.06. The highest densities of turtles (as derived from the Marsh and Sinclair (1989) method) were observed during D2 at C1 (0.96/km2). High turtle densities were observed primarily within the Darwin Outer region of IM block, within the areas of East Point, Lee Point and Gunn Point and within the western edges of Cox Peninsula. There were, however, high densities observed within Darwin Harbour Inner, specifically East Arm and Middle Arm.

The complete Dredging Phase results of the TDMP are reported in the Turtle and Dugong Monitoring Program Dredging Reports (Cardno 2013b-d, 2014b) and End of Dredging Report (Cardno 2014c).

1.5 Objectives The key objectives of the TDMP were to:

> Quantify the variability of turtle and dugong relative abundance and distribution in the inshore waters of Darwin Harbour and nearshore waters between and within surveys. Observe changes in these parameters over the duration of the Dredging and Post-dredging Phases; and

> Assess fine-scale aspects of dugong and turtle populations within Darwin Harbour in relation to potential habitat use and identify foraging areas (if possible).

This report focuses on results from Post-Dredging Phase aerial (P1; July 2014 and P2; October 2014) and land-based surveys (P2; October 2014) collected during the 2014 dry season. Where appropriate, comparisons were made with all previous Baseline and Dredging Phase aerial and land survey data to assess for any apparent patterns of change in dugong or turtle abundance and distribution.



2 Methodology

Specific details on the methodology used in the TDMP for aerial and land-based surveys are described in Appendix K of the Nearshore Environmental Monitoring Plan (NEMP; Rev 5) (Cardno 2014a) and the TDMP Baseline Report (Cardno 2013a). Turtle tagging methods are outlined in the Dredging Report 1 (Cardno 2013b). Where methodology has been refined, or where additional analyses have been utilised for Post-dredging Phase surveys, details have been provided in this report.

2.1 Field Monitoring Schedule Table 2-1 outlines the monitoring schedule for the TDMP during the Baseline, Dredging and Post-dredging Phases. Aerial surveys were undertaken during the dry season for all Baseline, Dredging and Post-dredging Phase surveys. The dry season is the optimal time of the year to undertake aerial surveys as there is less chance of unfavourable weather (rain, wind etc.) which can compromise visibility and influence availability bias.

Boat surveys (transect and point sampling) were carried out during the Baseline Phase only, while land-based surveys (point sampling) were undertaken during all Dredging Phase surveys and one Post-dredging Phase survey, in accordance with the NEMP (Cardno 2014a).

Turtle satellite tagging was initially undertaken in October 2012 and November 2012 at Channel Island and in October 2012 at Casuarina Beach, where an attempt was made to tag nesting flatback turtles. Additional tagging events were also undertaken at Channel Island in November 2013 and December 2013.



Table 2-1 Monitoring schedule for the TDMP

Sampling Periods

Baseline Phase Dredging Phase Post-dredging Phase

Field Method Site B1 B2 B3 D2 D3 D4 D5 P1 P2

Aerial surveys

Darwin Harbour and surrounding waters

1 to 8 June 2012 2 replicate flights

18 July 2012 to 5 August 2012 3 replicate flights (C1, IM, C2)

29 September 2012 to 21 October 2012 3 replicate flights (C1, IM, C2)

11 to 23 May 2013 3 replicate flights (C1, IM) 2 replicate flights (C2)^

27 July 2013 to 10 August 2013 3 replicate flights (C1, IM, C2)

13 to 27 October 2013 3 replicate flights (C1, IM, C2)

10 to 24 May 2014 3 replicate flights (C1, IM) 2 replicate flights (C2)^

8 to 20 July 2014 3 replicate flights (C1, IM, C2)

11 to 20 October 2014 3 replicate flights (C1, IM, C2)

Boat surveys

Darwin Harbour and surrounding waters

30 June 2012 to 6 July 2012

Transects and Point-sampling 1 replicate

2 to 15 August 2012

Transects and Point-sampling 2 replicates

1 to 10 October 2012

Point-sampling 2 replicates

-- -- -- -- -- --

Land-based surveys

Channel Island Bridge and Cullen Bay rock wall

-- -- -- 20 and 26 May 2013 2 replicates

30 July 2013 and 3 August 2013 2 replicates

15 and 23 October 2013 2 replicates

14 and 16 May 2014 2 replicates

-- 14 and 23 October 2014 2 replicates

Turtle satellite and flipper tagging

Channel Island Bridge -- --

16 to 21 September 2012 14 to 17 November 2012

-- --

5 to 7 November 2013 3 to 6 December 2013

-- -- --

Casuarina Beach -- --

16 to 28 September 2012

-- -- -- -- -- --

Nightcliff Jetty -- -- -- -- -- -- 27 March

2014* -- --

^ Reduced replicates due to unfavourable weather conditions. * Opportunistic satellite tagging event of a rehabilitated turtle, denotes date of release.



2.2 Field Sampling Locations

2.2.1 Aerial Surveys

During P1 (July 2014) and P2 (October 2014), aerial surveys were used to collect data over a broad spatial scale within three geographical locations (or blocks) (Figure 2-1):

> Control location 1 – C1 (Bynoe Harbour);

> Impact location – IM (Darwin Harbour/Hope Inlet to Gunn Point); and

> Control location 2 – C2 (located to the east of Darwin Harbour, from Gunn Point, around the Vernon Islands and across to Melville Island).

2.2.2 Land-based Surveys

In order to assess fine-scale aspects of the ecology of turtle and dugong populations, such as behaviour and movement of individuals in relation to frequently utilised habitats or ‘hotspots’ within Darwin Harbour, land-based surveys were undertaken during P2 (October 2014) from two locations: Channel Island Bridge and the rock wall at Cullen Bay (Figure 2-2).

2.2.3 Turtle Tagging

Tagging was initially attempted on nesting female flatback turtles at Casuarina Beach in September 2012 and juvenile turtles occurring near Channel Island Bridge in September 2012 and November 2012. Further attempts to tag juvenile turtles to assess patterns of movement and habitat utilisation around Darwin Harbour were undertaken in November 2013 and December 2013. Juvenile green turtles tagged were all captured in the northern channel adjacent to Channel Island in Darwin Harbour Inner (Figure 2-2; refer to Cardno 2013a,b, 2014c for more details on capture and tagging methodology).

Strandings of turtles can occur as a result of predatory attack, vessel strike, entanglement or as a consequence of unknown injuries. Turtles are occasionally found stranded around Darwin and many of these individuals are rehabilitated (primarily at Ark Animal Hospital, Palmerston, NT) and subsequently released near the location of capture/stranding. During the TDMP, any turtles that had been held for rehabilitation by appropriate veterinary clinics (e.g. Ark Animal Hospital) were assessed for possible inclusion in the tagging component of the monitoring program.



Aerial survey blocks and sub-divisions encompassing Bynoe Harbour (C1), Darwin Harbour/Hope Inlet region (IM) and Vernon Islands (C2) Figure 2-1



Land survey sites in Darwin Harbour during P2 (October 2014); Cullen Bay rock wall (left); and Channel Island Bridge (right), also showing Figure 2-2

the turtle tagging site



2.3 Field Methods The field sampling protocol utilised throughout the TDMP follows the methodology outlined in the NEMP (Rev. 5; Cardno 2014a).

2.3.1 Monitoring Permits

The TDMP was undertaken under an Animal Welfare Licence (No. 041, Animal Welfare Act Section 33 (2)) and Permit to Interfere with Protected Wildlife (Permit No. 44020, Territory Parks and Wildlife Conservation Act 2006). Animal Ethics Approval (turtle tagging) was obtained in October 2012 (Animal Welfare Act, Section 30, and Macquarie University AEC Reference No. 2012/036-2). Department of Land Resource Management (DLRM) and Fisheries S17/3282 special permits were also obtained.


Post-dredging aerial surveys were undertaken from 3 July 2014 to 21 July 2014 (P1), and 9 October 2014 to 24 October 2014 (P2), in a Dornier 220 (a high winged, twin prop, turbo engine aircraft), flown by two pilots at a speed of approximately 110 knots and at an altitude of 500 feet (152 m). During P1 and P2, three replicate flights were completed in each of the three main survey blocks (C1, IM and C2; Figure 2-1); however due to the challenging weather conditions experienced during P1 (refer to Section 4.1.1 for further details), this data was considered unsuitable for analysis.

Each survey followed a traditional strip transect survey design technique, as described by Marsh and Sinclair (1989). Each strip transect width was 200 m on each side of the aircraft, on which two tandem teams of two observers operated (i.e. a tandem pair on the both the port and starboard sides of the aircraft, each comprising a front and rear observer, making up a team of four observers). Each observer’s window was demarcated into four horizontal transect zones, which corresponded with areas (or sub-strips) of water within the strip transects (Low: 0 m to 50 m from the ground position of the aircraft; Medium: 50 m to 100 m; High: 100 m to 150 m; and Very High: 150 m to 200 m; see Figure 2-3). These transect zones were referred to when recording sighting locations over the aircraft audio system. Sightings on the ‘inside’ or the ‘outside’ of these zones, which refers to sightings inside (In) or beyond (Out) the 200 m transect width either side of the plane, were also recorded.

During most aerial surveys undertaken during the TDMP (B1 to B3, D2, D4 and P2), each transect followed an approximate north-east to south-west alignment (Figure 2-1), spaced equally at 2 km intervals, which minimised the chance of sighting the same animal twice, while maximising the aerial coverage (approximately 20%) of the survey block. However, during D3, D5 and P1, the orientation of transects within the C1 and C2 blocks were slightly altered where necessary to accommodate for excessive glare off the sea surface. All replicate flights flown within the IM block were flown in a north-east to south-west alignment at 2 km intervals, regardless of the time of day, due to restrictions enforced by Darwin Air Traffic Control.

Environmental and water variables (BSS, glare and turbidity based on a standardised scale used in aerial surveys by Hodgson et al. (2011)) were also recorded at the start and end of each transect and when these conditions changed notably during transects or for each sighting. As the waters around the Darwin region are generally turbid, turtle and dugongs are generally visible during aerial surveys only when they come to the surface to breathe. Sightability is therefore increased during calm seas when there are no other surface disruptions, and as such, aerial surveys were generally not carried out when conditions were persistently above a BSS of 3. Dugongs, turtles, dolphins and any incidental megafauna sightings (e.g. sharks, rays, sea snakes, crocodiles etc.) were recorded in each aerial survey. It should be noted that dolphins and other incidental megafauna sightings are not reported as part of the TDMP. Further details of the aerial survey methods are given in the TDMP Baseline Report (Cardno 2013a) and NEMP (Cardno 2014a).



Plane window calibration for aerial surveys (top dotted line = upper limit of Very High Figure 2-3zone; bottom dotted line = lower limit of Low zone)


Land-based surveys during P2 (October 2014) were undertaken from Channel Island Bridge and the Cullen Bay rock wall (Figure 2-2). At each site, a maximum of four hours of active observation was undertaken per day over two days, which included eight 30-minute observation periods separated by ‘off-effort’ windows. Observation periods were initiated only when the BSS was less than or equal to 3, which maximised the ability to sight marine megafauna. During each 30-minute observation period, observers scanned the water continuously (aided by polarised sunglasses) and assessed any surface disturbance with binoculars to identify the presence of any species of interest. When megafauna were sighted, the following data were recorded:

> Date and time of each sighting (if more than one animal was sighted at any one time, the priority was to gather data for the first animal sighted);

> Animal type: turtle, dugong, dolphin or other incidental sightings (including an identification ranking of certain, probable or uncertain); species identification was also attempted, and then ranked as certain or uncertain;

> Number of individuals (where multiple individuals were involved in a sighting);

> Bearing of sighting from the observer (using a hand-held compass or inbuilt compass in the binoculars);

> Estimated distance from the observer to the sighting; and

> Behavioural activity (e.g. foraging or travelling) or sighting cue (e.g. splash, head or back).

Environmental and water variables (BSS, glare and turbidity based on Hodgson et al. 2011) were recorded at the start and end of each observation period, while the position of each observer was recorded using a hand-held GPS. Average BSS and turbidity, representing the mean of the values recorded by the two observers at the start and end of each observation period, was calculated for the first and second replicate surveys i.e. day one and day two. It should be noted that dolphins and other incidental megafauna sightings are not reported as part of the TDMP.

2.3.3.1 Channel Island Bridge Two observers recorded observations of megafuana concurrently during each survey at Channel Island Bridge (Figure 2-2). One observer was positioned on the northern side of the bridge observing north, while the second observer was located on the southern side of the bridge observing to the south. Each observer was situated in the middle of the bridge (slightly offset to avoid traffic) and recorded observations of megafauna over the entire width of the channel on their side of the bridge.



2.3.3.2 Cullen Bay Rock Wall Two observers situated at the fork of the rock wall at Cullen Bay (Figure 2-2), recorded observations of megafauna concurrently: one observer recorded observations in the east to north quadrant (i.e. towards Fannie Bay) and the other recorded observations in the west to north quadrant (i.e. including Cullen Bay).

2.4 Assumptions and Constraints


Aerial surveys are widely used to estimate the distribution and relative abundance of marine megafauna over relatively large spatial and temporal scales. This approach assumes that the ability to sight dugongs and turtles is largely dependent on water turbidity and sea state. Changes in densities over time can also be estimated and these are useful indices of changes in abundance, as long as biases are held constant by rigid standardised techniques.

During P1 (July 2014), despite clear weather conditions and greater water visibility early in the survey period, an increase in unpredictable weather and excessive winds resulted in unsuitable survey conditions later in the field period. This was specifically evident during C1 replicate flight one (Beaufort Sea State (BSS) ≤ 6) and IM block replicate flights three and one (BSS ≤ 5 and 6 respectively). Prevailing winds during morning periods resulted in some flights having to be flown in late afternoon which increased the effect of glare due to the angle of the sun. Therefore, to minimise the effect of excessive glare, which could potentially impede the observability of animals, the orientation of transects flown during C1 and C2 replicate flights one were changed to a north-west to south-east orientation (as opposed to north-east to south-west). Due to the challenging conditions experienced during most of the P1 survey, these data were not included in analyses (refer to Section 4.1.1 for more details).

Taking into consideration the challenging environmental conditions experienced intermittently throughout the P1 survey, whereby the desired nine replicate flights were unable to be completed, combined with near ideal conditions experienced during the P2 survey, caution should be taken when comparing between Post-dredging Phase and certain Baseline and Dredging Phase surveys due to the difference in the number of replicate flights for each survey.

Given the large tidal range characteristic of the Darwin region, it is likely that tidal conditions experienced during aerial surveys may have had an influence on the overall sightability of both turtles and dugongs and hence the number of animals sighted. The visibility of animals, especially around reef habitats, generally increased during lower tidal periods as submerged animals were able to be seen across the reef platforms and, in some cases, are seen to be actively foraging in these areas. However during high tidal periods these reef habitats were no longer visible due to the greater water depth, and therefore, animals that may have occurred in these habitats were no longer available to an observer.


During land-based surveys neither the species of turtle nor any identifying characteristics (e.g. scars, deformities) of most individual turtles or dugongs were able to be recognised from the viewing location so it was likely that some animals were counted more than once. Therefore, it is probable that the total number of sightings for a given site recorded during sampling events was higher than the actual number of individuals present. Furthermore, by having a relatively large area to observe (particularly at Channel Island Bridge), there was also the potential that some sightings were missed as the whole area cannot be scanned by the observer simultaneously.

Tidal movements are also likely to have impeded the number of sightings during land-based surveys, particularly at Channel Island Bridge, where intertidal reef platforms are periodically exposed during extreme low tides (especially during spring tides). While the shallow water increases sightability of turtles in the area, it appeared turtles actively remained off the reef platform to avoid being stranded. Similarly, strong tidal currents through the channel may increase the effort required by turtles to forage on shallow reef platforms during running currents, thereby making foraging activities more difficult and as a result, may have affected the number of turtles seen around the bridge.




Deploying a net was determined to be a more appropriate means of turtle capture than the rodeo method due to additional safety measurers required when monitoring in Darwin Harbour. While the rodeo capture method, which involves diving into the water and physically catching the turtle, may have enabled more turtles to be caught, the bathymetry, lack of in-water visibility, presence of crocodiles and box jelly fish and other safety issues associated with this method made it unsuitable for the TDMP.

Despite modifications to minimise the visibility of the net to turtles, some turtles were able to detect the net and subsequently avoid capture. It was also found that turtles were able to release themselves from the net following entanglement. These factors contributed to the small number of turtles caught during the TDMP (refer to Cardno 2013a-d, 2014b,c for more details on capture and tagging methodology).

2.5 Data Analysis


2.5.1.1 Distribution and Habitat Use For each turtle or dugong sighting, the corrected instantaneous water depth was determined by estimating the vertical difference between the tidal water level and the underwater bed strata depth based on the calculated GPS location of the sighting. This involved combining the tidal height at the time and position of each sighting (relative to mean sea level) and the bed strata depth at that position (also relative to mean sea level). The tidal level at the time of each sighting was obtained from predicted tides for the Darwin area which is provided by the National Tidal Centre. Spatial variation among the survey blocks in the heights and timing associated with the tidal cycle was assumed to be negligible, although it is acknowledged that variations do exist.

The bed strata depths were determined using two different bathymetric data sets, with the primary source being the Australian Hydrographical Service nautical charts (Australian Hydrographic Service 2003, 2007, 2009a, b). For sightings outside the boundaries of these charts, depths were sourced from the Geoscience Australia Bathymetry and Topography Grid (Whiteway 2009), which has a 250 m grid cell resolution.

Corrected instantaneous water depths were rounded to one decimal place and sightings were assigned to one of five depth categories, defined as:

> 0 m to 5 m (0 m to 5.9 m);

> 6 m to 10 m (6.0 m to 10.9 m);

> 11 m to 20 m (11.0 m to 20.9 m);

> 21 m to 30 m (21.0 m to 30.9 m); and

> ≥ 31 m (≥ 31.0 m).

Benthic habitat was determined for each sighting from habitat maps of the Darwin region. These maps were developed primarily from data collected for the draft Environmental Impact Statement for the Project (INPEX 2011), in conjunction with other subtidal and intertidal maps of hard coral, macroalgae, filter feeder and seagrass communities on the reef and sediment substrata in the Darwin region. The GPS locations for each turtle or dugong sighting were able to be overlaid with this spatial data to determine the benthic habitat present at each location. Habitat types were categorised as:

> Sand;

> Reef (includes reef mixed communities, macroalgae, filter feeders and hard coral);

> Seagrass;

> Mangrove;

> Gravel;

> Mud;

> Rock; and



> Unsurveyed (areas in the blocks where the type of benthic habitat had not been determined in habitat maps).

2.5.1.2 Dugong and Turtle Population Estimates and Densities Population estimates of dugongs and turtles for each survey block (C1, IM and C2) were calculated separately using two different methods: the Marsh and Sinclair (1989) method and the Pollock et al. (2006) method. The Marsh and Sinclair (1989) method uses estimates of availability and perception biases averaged for each aerial survey and corrects for differences in sighting conditions between surveys. By contrast, the Pollock et al. (2006) method accounts for differences in sighting conditions for each sighting.

Population estimates were based on the estimated number of animals (turtles or dugongs) for each tandem team per transect, which were corrected by the appropriate correction factors (perception and availability bias), mean group size (i.e. mean number of animals in sighted groups) and density (number of sightings per km2). Both methods attempt to correct for availability bias (animals not available to observers because of water turbidity) by applying availability correction factors (ACFs) and perception bias (animals visible in each transect but missed by observers) by applying perception correction factors (PCFs). However, spatial heterogeneity in sighting conditions among observations was only addressed by the ACF associated with the Pollock et al. (2006) method. The Marsh and Sinclair (1989) ACF method averages conditions within each replicate flight for each spatial block (or sub-block) and only corrects for differences in availability bias between spatial or temporal partitions (i.e. blocks or surveys).

Where possible, dugong and turtle population estimates were calculated for each block (n = 3) using both of the methods. Due to limited dugong sightings throughout the TDMP, population estimates for sub-blocks (n = 14) were calculated for turtles only. For the turtle population estimate calculations, blocks were further partitioned into sub-blocks (C1 – four sub-blocks; IM – six sub-blocks; C2 – four sub-blocks), each of which comprised areas of similar bottom type and bathymetry, such as intertidal, inshore or offshore. While population estimates can be calculated based on any number of sightings, the variances associated with calculations are large, therefore reducing the reliability. As such, only replicate flights in Post-dredging Phase surveys which included more than five sightings were used for population estimates, as this has been consistent protocol across all flights throughout the TDMP.

To calculate PCF values for the Marsh and Sinclair (1989) method and for modelling of perception bias in MARK (a program that provides parameters used to estimate population size for the Pollock et al. (2006) method), data were pooled by block instead of by replicate flight. The latter was undertaken for surveys completed prior to D3 (July 2013). For these calculations in D3, D4, D5, P1 and P2 surveys, aerial transect data were able to be pooled within blocks given the observer team was consistent across all replicate flights and the order of transects flown was determined haphazardly and based on environmental conditions, as opposed to a strict, structured order prior to D3. As for previous analyses, group size and corresponding Coefficient of Variation (CV) values were determined for each replicate flight. Values of CV are used to compare the standard deviations between populations with different means and provide measures of variation that are independent of the measurement units.

Density estimates for dugongs and turtles were calculated by dividing the derived population estimates and raw sightings data by the total transect area sampled over water within each of the three blocks, 14 sub-blocks and 43 individual 6 km x 6 km grid cells that are overlayed within the IM block only. Furthermore, IM block grid cells were categorised as either Darwin Harbour Inner (grid cells 25, 26, 30, 31, 32 and 34 to 42 inclusive; n = 14 cells) or Darwin Outer (grid cells 1 to 24 inclusive, 27, 28, 29, 33 and 43; n = 29 cells (Figure 2-4).



Aerial survey density grid cells for Darwin Harbour/Hope Inlet area (IM) divided into Darwin Harbour Inner and Darwin Outer regions Figure 2-4



2.5.1.3 Statistical Analysis Population density estimates (number per km2) for dugongs and turtles for replicate flights undertaken in blocks and sub-blocks as derived from the Marsh and Sinclair (1989) population estimates, Pollock et al. (2006) population estimates and raw sightings data were analysed separately using permutational univariate analyses of variance (PERMANOVA; Anderson 2001), using Euclidean dissimilarity resemblance matrices with unrestricted data permutation methodology, to determine spatial and temporal differences.

The four factors used in the analysis of each density dataset were:

> Phase (fixed, orthogonal): 3 levels (Baseline, Dredging and Post-dredging);

> Survey (random, nested within Phase): B1, B2 and B3 within Baseline Phase; D2, D3, D4 and D5 within Dredging Phase; and P2 for the Marsh and Sinclair (1989) and Pollock et al. (2006) methods and P1 and P2 for the raw sighting method within the Post-dredging Phase;

> Treatment (fixed, orthogonal): 2 levels (Impact – IM and Control – C1 and C2); and

> Block (random, nested within Treatment): IM within Impact treatment; and C1 and C2 within Control treatment.

Where a term (factor or interaction) was significant at p ≤ 0.05, pair-wise comparisons were used in post-hoc analyses to identify which levels of factors or interaction strata were significantly different. Blocks for which fewer than two replicate flights were available for analysis (i.e. due to ≤ 5 sightings in two or more of the three replicate flights) were not included in the analyses.


Variability in the land-based surveys compromised the potential for formal analyses to detect any spatial differences and/or temporal changes in abundance of dugongs and turtles. Factors affecting variability included observing conditions (e.g. BSS, turbidity and glare), tidal movements and temporal changes in the distribution and movements of the animals themselves. Land-based data have, therefore, been presented in a tabular format with spatial representation of sightings in the form of GIS mapping.


Data on the location, length and duration of dives by satellite tagged turtles were downloaded weekly from ARGOS Worldwide Tracking and Environmental Monitoring Systems (www.argos.com or Seaturtle.org), which provided both ARGOS and Fastloc GPS positions and histogram dive data. ARGOS location points are based on seven levels of accuracy, denoted by a location class (LC) of numerical or alpha value. LC-3 is most accurate with a given error of < 150 m; LC-2 has an error of 150 m to 350 m; LC-1 has an error margin of 350 m to 1000 m; and LC-0 has an error > 1000 m. Alpha LC values (A, B and Z) and LC-0 are the most commonly received, although these locations do not include error estimates.

Development of Fastloc GPS technology (hardware developed by Wildtrack Telemetry Systems Ltd, United Kingdom) has allowed simultaneous collection of GPS and ARGOS locations from tagged marine fauna. Fastloc GPS is able to obtain GPS satellite data in less than 100 m by capturing satellite signals, identifying the relevant satellites and calculating their pseudo-ranges, before transmitting the data through the ARGOS system. A higher number of satellite signals enable greater accuracy when giving GPS locations, with nine satellites giving very accurate location data, and less than four often not being able to give a GPS position (these data are discounted for plotted locations).

The accuracy of Fastloc GPS locations have been found to be far greater than the ARGOS positions (Costa et al. 2010), and thus these tracks were used for all spatial representation of turtle movements in the form of GIS mapping for the TDMP. Dive duration and depth data have been compiled in Excel and are presented in graph format for comparison among individual turtles. Satellite transmissions for the last remaining tagged turtle as part of the TDMP ceased on 9 August 2014 (refer to Section 4.4).

2.6 Quality Assurance/Quality Control (QA/QC) Species sighting and environmental data from each survey were transcribed and entered into a Microsoft Access database post-flight by each observer and the environmental data collector. As part of the process,



10% of all entries were randomly checked by each tandem team. If any errors were found, a further 10% of records were checked. Any errors were subsequently rechecked and amended in the database before data compilation and analysis. Once all datasets were compiled, the final QA process was undertaken on data in a master database by the Team Leader, where a further 10% of the total number of transects flown were randomly checked. If any errors were found, a further 10% of transects were checked.

Land survey data were recorded on datasheets in the field and entered into an Excel spread sheet at the end of each survey by each team. All entries were checked for completeness against field datasheets and any missing cells or information was amended where necessary. As part of the QA process, 10% of records were then checked for errors by random selection. If any errors were found, a further 10% of records were checked, with all errors amended before further data compilation and analyses were completed.



3 Dredging Operations

The dredging program involves a number of dredge vessels including BHDs, CSD and trailing suction hopper dredgers (TSHDs) operating in different areas depending on water depths, bed material characteristics and the volume of material to be removed.

The EA dredging campaign is divided into five dredging footprint separable portions (SP1 to SP5), which refer to the location and duration of specific dredging activities. The SPs are summarised in Table 3-1 and presented in Figure 3-1.

Season One of the dredging campaign commenced on 27 August 2012 with BHDs, while CSD operations commenced 4 November 2012, with all Season One dredging operations ceasing on 30 April 2013. The dry season dredging hiatus extended from 1 May 2013 to 31 October 2013. Season Two of the EA dredging campaign commenced on 1 November 2013 and finished on 11 June 2014, while the GEP dredging program commenced on 23 October 2013 and concluded on 12 July 2014.

Table 3-1 Dredge footprint summary

ID Separable Portion

SP1 Separable Portion 1 − Module Offloading Facility (MOF)

SP2 Separable Portion 2 − Jetty Pocket

SP3 Separable Portion 3 − Berth Area

SP4 Separable Portion 4 − Approach Channel, Berth Approach and Turning Area

SP5 Separable Portion 5 − Walker Shoal



EA dredging footprint and GEP routeFigure 3-1



4 Results

This section presents the results of the P1 (July 2014) and P2 (October 2014) aerial survey and P2 land survey. Where appropriate, aerial and land survey data are compared to Baseline Phase (B1; May 2012, B2; July 2012 and B3; October 2012) and Dredging Phase (D2; May 2013, D3; July 2013, D4; October 2013 and D5; May 2014) surveys. Detailed results of these individual surveys are provided in previous TDMP reports (Cardno 2013a-d, 2014b,c).

4.1 Aerial Surveys

4.1.1 Survey Effort and Environmental Conditions

During P1, three replicate flights were completed for each block, with C1 Rep 1 and C2 Rep 1 flown in a north-west to south-east alignment in order to minimise excessive glare. All other flights over C1, C2 and IM were flown in a north-east to south-west orientation as per TDMP protocol (Section 2.3.2).

In alignment with aerial survey conventions, the NEMP states that aerial surveys carried out as part of the TDMP will not be conducted in conditions of BSS > 3 to maximise sightability of animals (Cardno 2014a). In general, small periods over the duration of a flight, often no more than 1 minute at a time, where BSS has been > 3 have been acceptable; however, when BSS > 3 occurred for long periods of a flight, the flight has either been abandoned before completion, or post-flight, data has been assessed for its suitability in analysis.

The environmental conditions throughout P1 were highly variable, with BSS recorded across all flights ranging between 0 and 6. While some flights (C2 Reps 1, 2 and 3, and C1 Rep 2) were carried out under adequate conditions within a BSS range of 1 to 4 (where only small patches of BSS = 4 were observed), unpredictable and excessive wind conditions during the remaining flights resulted in large sections of the replicate flights where BSS was 4 and 5, and up to 6 in some small patches (C1 Rep 1 and IM Rep 1). This was particularly evident in the outer transects of both the C1 and IM blocks where waters were more exposed to prevailing winds.

The BSS associated with each sighting is taken into account in the Pollock et al. (2006) model for estimating population sizes, so that when sightings are made in elevated sea states (along with other factors) estimates will be driven higher. Consequently, this will cause a bias in the estimates derived which is not necessarily affected by the numbers of animals seen.

Taking these factors into consideration, it was determined that data collected during P1 replicate flights with BSS values greater than 3 were unsuitable for analysis. As a result, only minimal data remained for P1, and so it was further determined that analyses for the Post-dredging Phase excluded P1 data altogether. Only raw sighting data for P1 have been included in Sections 4.1.2.3 and 4.1.3.3 for reference, and in the statistical analysis of raw sightings (Table 4-4).

During P2, all flights of C1, IM and C2 were flown in the north-east to south-west orientation, with three replicate flights of each block completed. A total of 4,075 km of linear transects were sampled over a cumulative time period of approximately 20 hours. The total length of transects flown ‘over water’ of one replicate flight for each block (blocks combined) was 1,358 km, equating to a sampled area of 543 km2

(based on a transect width of 400 m spanning both sides of the plane). This represented approximately 20% of the total available area within the three blocks. The overall area surveyed across all three geographical blocks per replicate flight (variable due to tidal level) was 2,697 km2 (Appendix A).

Environmental conditions recorded during P2 were generally consistent (mean BSS = 2.1, range 0 to 4), with the mean BSS for individual flights ranging from 1.4 in C2 Rep 2 to 2.8 in C2 Rep 3; and turbidity, based on Hodgson et al. 2011, ranged between 1 and 4, with an average of 3.7. All replicate flights for P2 were suitable for use in analysis.



4.1.2 Dugongs

4.1.2.1 Sightings and Distribution During P2, 77 dugongs were observed across all three blocks, over nine replicate flights (C1: n = 10 dugongs, 3 Reps; IM: n = 49, 3 Reps; C2: n = 18, 3 Reps; Appendix B), during one of which there were 30 individual dugongs sighted (IM Rep 3). This total for P2 was consistent with the survey average for dugong sightings over the whole monitoring program (79 ± 8) and is comparable to numbers observed during surveys carried out previously during the same time of year (B3 (October 2012), n = 113; D4, n = 87; Appendix B).

Dugongs sighted during P2 were predominantly adults, consistent with all aerial surveys undertaken during the TDMP. Eight calves were sighted during P2, with one calf in C1, three in C2 and four in IM. This represents the highest number of calf sightings over the entire monitoring program, followed by B2 and D4 where seven calves were observed during each survey, five of which were sighted in the IM block on each occasion (Appendix B). The least number of dugong calves observed during the TDMP was in C1, with four sighted in total, including one calf in each of the B1, D3, D5 and P2 surveys. Overall, there were 12 and 20 calf sightings in C2 and IM respectively, with no calves sighted in C2 during B3 and D2, and in IM during D5.

The spatial distribution of dugongs has varied greatly between Baseline, Dredging and Post-dredging Phase (P2 only) surveys (Appendix B). Dugongs have been predominately sighted in the Darwin Outer region (n = 282 dugongs), with few sightings through Darwin Harbour Inner (n = 41 dugongs) during the monitoring program (Cardno 2013a-d, Cardno 2014b,c).

In Darwin Harbour Inner during the Baseline Phase, there were 30 dugongs sighted, specifically in Fannie Bay, East Arm and just north of East Point in B1 (n = 9), Weed Reef, West, Middle and East Arms in B2 (n = 19), and near Fannie Bay and just east of Weed Reef in B3 (n = 2). In Darwin Outer there were 103 dugongs sighted during the Baseline Phase, with consistent sightings through Shoal Bay up to Gunn Point and varying numbers around Casuarina Beach and Lee Point near mapped seagrass habitat (GeoOceans 2012).

During the Dredging Phase, few dugongs were sighted in Darwin Harbour Inner (n = 9), with sightings around Middle Arm and Weed Reef in D2 (n = 2), Fannie Bay and Woods Inlet in D4 (n = 2) and Weed Reef and Fannie Bay in D5 (n = 5). There were no dugongs sighted in Darwin Harbour Inner during D3. In Darwin Outer, 132 dugongs were sighted during the Dredging Phase, and similar to Baseline Phase surveys, dugongs were regularly sighted throughout Shoal Bay and at varying frequencies around Casuarina Beach and Lee Point.

Similarly, during the Post-dredging Phase (P2 survey), there were few dugongs sighted in Darwin Harbour Inner (n = 2) with sightings in West Arm and off the Larrakeyah naval base. There were 47 dugongs sighted in Darwin Outer during the Post-dredging Phase, mainly concentrated between East Point and Lee Point, with few sightings in Shoal Bay.

The spatial distribution of dugongs in P2 generally matched the distribution pattern of dugongs during previous surveys carried out at a comparable time period (B3 and D4), with aggregations observed mainly between East Point (seaward margin of Darwin Harbour Inner) and Lee Point (IM) and near Melville Island (C2). There were limited sightings near the Vernon Islands and within the inlet between Gunn Point and Cape Hotham in the C2 block. Furthermore, there were few sightings within Shoal Bay and in areas off the western edge of the Cox Peninsula and north of Mandorah in the IM block. For areas within C1, dugongs were sparsely distributed around the islands to the west of Bynoe Harbour, with a few sightings of north of Indian Island (Figure 4-1). For surveys undertaken in the month of October (B3, D4 and P2), in the areas of the IM block in Darwin Outer, sightings have been concentrated between East Point and Lee Point and around Casuarina Beach.

The highest density of dugongs recorded in the IM block during P2 (based on raw sightings within designated 6 km x 6 km grids) occurred between East Point and Lee Point (grid cells 19 (2.6 per km2) and 20 (2.2 per km2) respectively) (Figure 4-2). This spatial pattern is similar to that observed in previous surveys during the same temporal period in 2012 (B3) and 2013 (D4) with the highest density of dugongs occurring in grid cell 20 for both surveys (3.7 per km2 and 2.7 per km2 respectively) (Cardno 2013b, 2014b). In P2, lower densities of dugongs were sighted through Shoal Bay, primarily on the eastern side, ranging from 0.3 per km2 in grid cell 28 to 1.7 perkm2 in grid cell 24, which again was similar to the location of dugongs sighted



during the previous October surveys (B3 and D4). During B3 and D4, dugongs were also sighted around Cox Peninsular (ranging between 0.2 per km2 and 1.4 per km2 in grid cells 43 and 1 during B3, and 0.3 per km2 and 0.9 per km2 in grid cells 1 and 9 during D4); however no dugongs were sighted in this area during P2 (Figure 4-2).

Compared with previous surveys carried out at a similar time of year (B3 and D4), the density of dugongs sighted during P2 increased by more than 0.2 dugongs per km2 since B3 in 16% of IM grid cells, and decreased by approximately 0.2 dugongs per km2 in 12% of grid cells (Figure 4-3). A relatively small change (between -0.2 and 0.2 dugongs per km2) between P2 and B3 was evident in 72% of IM grid cells. Dugong densities were zero in P2 and B3 in approximately half of the IM area (51%), which incorporates both the Darwin Harbour Inner and Darwin Outer regions (Figure 4-3). Dugong densities during P2 increased by more than 0.2 dugongs per km2 in 14% of the IM grid cells compared with D4 (Figure 4-4), and decreased by more than 0.2 dugongs per km2 in 14% of IM grid cells. Between P2 and D4, a relatively small change (between -0.2 and 0.2 dugongs per km2) was detected in 72% of IM grid cells, with dugong densities of zero in 58% of IM grid cells during both P2 and D4. Across all surveys in the monitoring program, no dugongs were sighted in 10 of the 43 IM grid cells; within Darwin Outer (grid cells 6, 13, 17, 27 and 33) and Darwin Harbour Inner (grid cells 32, 35, 36, 37 and 41).



Distribution of dugongs (based on raw sightings) among and within sub-blocks during P2 aerial surveys (three replicate flights of C1, IM Figure 4-1

and C2)



Density of dugong sightings (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids at IM during P2 Figure 4-2

(October 2014)



Relative difference in dugong density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM Figure 4-3

during P2 (October 2014) compared with B3 (October 2012)



Relative difference in the dugong density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids at IM Figure 4-4

during P2 (October 2014) compared with D4 (October 2013)



4.1.2.2 Dugong Bathymetric Distribution and Habitat Associations During P2, the majority of dugongs (84%) were sighted in waters shallower than -11 m LAT, with a maximum depth of -32.7 m LAT in the C2 block. Of the 77 dugongs sighted across all three blocks during P2, 68% occurred in waters ≤ -5 m LAT, 17% in waters -6 m to 10 m LAT, 10% in waters -11 m to -20 m LAT and 3% in each of the -21 m to -30 m LAT and ≥ -31 m LAT depth categories. For total numbers of dugongs sighted in each block and survey, refer to Appendix B.

There was considerable spatial variation in the depth distribution of dugongs sighted across all blocks during P2. In C1, all dugong sightings were in waters up to and including -5 m LAT (Figure 4-5). This is similar to previous Baseline and Dredging Phase surveys where the majority of sightings occurred in the shallowest depth category. In the IM block, a pattern of decreasing occurrence with increasing depth was apparent, which was generally consistent with previous surveys. However, the decrease in sightings with depth observed during P2 was greater compared with previous surveys, with proportionally more dugongs sighted in the 0 m to -5 m LAT depth category (82%), followed by 14% and 4% of sightings in waters of -6 m to -10 m LAT and -21 m to -30 m LAT depth categories respectively. C2 varied greatly from both C1 and IM with the highest quantities of dugongs sighted in the -6 m to -10 m LAT and -11 m to -20 m LAT depth categories (33% and 44% respectively), while only 11% of dugongs were sighted in 0 m to -5 m LAT depths. Unlike C1 and IM, dugongs in C2 were also sighted in depths ≥ -31 m LAT (11%), similar to previous surveys, B2 (7%), B3 (11%) and D3 (15%). This is consistent with the general trend observed during the monitoring program (with the exception of B3 and D5), where a large proportion of sightings occurred in waters between -11 m and -20 m LAT. However, during P2, fewer sightings in C2 were made in the 0 m to -5 m LAT depth category than all previous Baseline and Dredging Phase surveys (i.e. 11% during P2 in comparison to a range between 16% (B1) and 33% (B2) in all previous surveys).

During P2, total dugong sightings for all blocks over sand and seagrass were similar (49% and 43% respectively). Proportionally fewer numbers of sightings were made over reef and mud habitats (4%for both habitat types). This represents the highest number of dugong sightings made within seagrass habitat compared with all previous surveys, which ranged from 0% in B2 (July 2012) to 14% in D4 (October 2013).

Patterns in the spatial distribution of dugong sightings within C1 and IM across different benthic habitat types were generally similar in P2 compared with previous surveys, while C2 showed more variability between sightings in specific habitat types than for previous surveys (Figure 4-6). During P2, dugong sightings in C1 occurred over either sand (50%) or gravel (50%) habitat types, which was consistent with habitat associations in C1 during previous surveys. Generally in C1, gravel was the dominant habitat type with more than 50% of sightings in B1, B3, D2, D3 and D5. During P2, the majority of dugongs sighted in IM block (61%) were observed over sand substrata, with a substantial number of sightings (31%) also made over seagrass habitat, which was comparable to previous surveys carried out during the same temporal period, B3 (October 2012) and D4 (October 2013) (22% and 26% respectively). Proportionally fewer sightings were made over reef and mud habitats, each accounting for 4% of sightings, with no sightings made over gravel substrate in contrast to all previous surveys (B1 (May 2012) to D5 (May 2014)). In C2, 67% and 22% of dugong sightings occurred over unsurveyed and gravel substrates respectively, with relatively few sightings in reef and sand habitats (6% attributed to each), unlike previous surveys where reef and sand habitats comprised a large proportion of sightings.



Proportion of dugong sightings within different depth ranges (m) below LAT in: a) C1; b) Figure 4-5

IM; and c) C2 for B1 (May 2012) to P2 (October 2014) surveys

N.B. P1 (July 2014) data are not presented, refer to Section 4.1.1

00.10.20.30.40.50.60.70.80.9

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0 - 5 6 - 10 11 - 20 21 - 30 ≥ 31

a) C1

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ong

sigh

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B2

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D3

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D5

P2

b) IM

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0 - 5 6 - 10 11 - 20 21 - 30 ≥ 31 Depth (m)

c) C2



Proportion of dugong sightings with respect to benthic habitat types at: a) C1; b) IM; and Figure 4-6

c) C2 for B1 (May 2012) to P2 (October 2014) surveys


00.10.20.30.40.50.60.70.80.9

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Mangroves Reef Sand Seagrass Gravel Mud Rock Unsurveyed

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ong

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B1B2B3D2D3D4D5P2

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1 c) C2



4.1.2.3 Dugong Population Size – Whole Blocks: Raw Sightings and Population Estimates Raw sightings in P1 are provided for context only in Figure 4-7c, noting data was considered unsuitable in P1 due to the challenging survey conditions experienced during this survey (refer to Section 4.1.1). Based on raw sightings, during P2 the mean number of dugongs sighted for each block was C1: 3.3 ± 1.9, IM: 16.3 ± 6.8 and C2: 6.0 ± 2.5 (n = 3 flights; Figure 4-7c).

Mean numbers of dugongs sighted in the Baseline Phase was generally consistent for C1 and C2, while in IM the means were more varied (Figure 4-7c). Comparatively, Dredging and Post-dredging Phase surveys showed a high degree of temporal and spatial variability. The mean number of dugongs sighted during D2 was lower at C1, IM and C2 compared to previous surveys, although subsequent surveys (D3 to D5) were generally comparable to Baseline Phase levels. The exception to this was at C2 in D5 where there was an increase. During P2, mean numbers of dugongs in C1 and C2 were somewhat comparable to previous surveys, while IM recorded the second highest mean number of dugongs after B3 (21.7 ± 11.6; Figure 4-7c).

Due to the small numbers of dugong sightings observed during the monitoring program, PCFs and ACFs were calculated using all sightings combined across blocks, while group sizes and CV were calculated for each replicate flight (Table 4-1). The estimates were based on all dugong raw sightings, including those in the ‘inside’ and ‘outside’ zones (refer to Section 2.3.2). During P2, the highest number of dugongs were sighted in replicate 3 of IM block (n = 30 individuals) across 21 group sightings. Furthermore, of the dugong groups sighted by port observers, 48% were observed by both observers, which is the highest compared to all TDMP surveys. For starboard side, 44% of the total number of dugong groups was sighted by both observers (Table 4-2).



Table 4-1 Details of group size estimates and correction factors used in dugong population estimates for P2 (October 2014) aerial surveys N.B. these parameters were used in the Marsh and Sinclair (1989) population estimate methods only: PCF – Perception Correction Factor; ACF – Availability Correction Factor; CV – Coefficient of Variation

Survey Block Replicate Mean group size (CV) PCF (CV) ACF (CV)

Total mean group size

(CV)

Starboard Port

P2

C1

1 2.00 (0.00)

1.17 (0.06) 1.11 (0.05) 3.27 (0.15) 1.43 (0.05)

2 1.00 (0.00)

3 1.40 (0.18)

IM

1 1.29 (0.14)

2 1.43 (0.14)

3 1.43 (0.10)

C2

1 1.60 (0.25)

2 1.80 (0.10)

3 1.00 (0.00)

Table 4-2 Sighting histories for dugong groups sighted during P2 aerial surveys by individual observers for all flights combined*

Block Rep Number of dugong groups seen by:

# dugongs sighted/ replicate

Total # dugong groups sighted

% dugong groups sighted by both observers

PF PR PB SF SR SB Port Starboard

C1

1 0 0 0 0 1 0 2 1 - 0%

2 0 0 1 0 0 0 1 1 100% -

3 3 1 0 1 0 0 7 5 0% 0%

IM

1 0 0 4 2 0 1 9 7 100% 33%

2 1 0 2 0 2 2 10 7 67% 50%

3 2 2 3 3 3 8 30 21 43% 57%

C2

1 2 1 1 1 0 0 8 5 25% 0%

2 2 0 1 1 1 1 9 6 33% 33%

3 0 0 1 0 0 0 1 1 100% -

Total 10 4 13 8 7 12 77 54 48% 44%

Port front (PF); port rear (PR); port both (PB); starboard front (SF); starboard rear (SR) and starboard both (SB). * All dugong sightings combined (given in Total) were used for estimates for PCF and MARK analysis in the P2 survey.



Due to highly variable environmental conditions experienced during P1 resulting in unsuitable data, population sizes for P1 were unable to be estimated (refer to Section 4.1.1). Further, due to low dugong sightings (≤ 5) during P2, population sizes for this survey could only be estimated for replicate flight 3 for C1 block, all replicate flights for IM block and replicate flights 1 and 2 for C2 block. The mean population estimate for dugongs in the C1 block during P2 (± SE) was calculated to be 123 ± 59 dugongs using the Marsh and Sinclair (1989) method, which is the lowest mean population size estimated for aerial surveys done in a similar period i.e. B3 (157 ± 112) and D4 (181 ± 84; (Table 4-3a, Figure 4-7a, Appendix D).

In comparison, calculations for the mean population size of dugongs for C1 using the Pollock et al. (2006) method was lower (61 ± 20) than those based on Marsh and Sinclair (1989), and comparable to D4 estimates (62 ± 27). Further comparisons showed that C1 block estimates during P2 were lower than Baseline Phase mean population estimates (190 ± 103; 167 ± 168) and Dredging Phase mean population size estimates (165 ± 63; 93 ± 44; Table 4-3b) calculated using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods respectively.

The mean dugong population estimates for P2 calculated using the Pollock et al. (2006) method were less than those calculated using the Marsh and Sinclair (1989) method across all survey blocks (C1: 61 ± 20, IM: 187 ± 104 and C2: 102 ± 47; (Table 4-3a, Figure 4-7b). This pattern was consistent for the Baseline and Dredging Phase surveys, with the exception of C1 population estimates during B2 where the Pollock et al. (2006) method provided a higher estimate (Figure 4-7a, b).

During P2, estimates of dugong population size in the IM block using the Marsh and Sinclair (1989) method were calculated for all replicate flights and although Rep 1 and 2 were similar (180 ± 116, 180 ± 96 respectively), Rep 3 estimates (559 ± 299) were higher. Mean population size estimates for dugongs in the IM block were estimated to be 306 ± 188, which is lower than estimates calculated for both of the corresponding time periods of B3 (401 ± 167) and D4 (382 ± 154; Table 4-3a). The P2 estimate of dugong population size in the IM block was greater than for B1 (243 ± 61), D2 (99 ± 48) and D5 (280 ± 79), but lower than B2 (411 ± 127), B3 (401 ± 167), D3 (315 ± 170) and D4 (382 ± 154; Figure 4-7a).

The P2 estimates of dugong population sizes in the IM block using the Pollock et al. (2006) method, ranged from 86 ± 29 (Rep 1) to 351 ± 131 (Rep 3) and the overall mean population size was estimated at 187 ± 104 (Table 4-3a, Figure 4-7a, b). The P2 estimates for C2 block using the Pollock et al. (2006) were calculated for Rep 1 and 2 only, with the mean population size estimated to be 102 ± 47. As for the estimates made using the Marsh and Sinclair (1989) method, this was the lowest mean population estimate for C2 across all survey periods, with the exception of D2 (67 ± 26).

When comparing overall mean population estimates between Phases (Baseline, Dredging and Post-dredging) for C1, estimates were higher during the Baseline Phase for both Marsh and Sinclair (1989) (190 ± 103) and Pollock et al. (2006) (167 ± 168; Table 4-3b) methods. For IM, the Post-dredging Phase (P2) was lower than the Baseline Phase (231 ± 138), but similar to the Dredging Phase (180 ± 80) for estimates based on Pollock et al. (2006). A similar trend was evident when assessing mean estimates for IM across all Phases based on Marsh and Sinclair (1989) methods (Baseline: 359 ± 154, Dredging: 305 ± 173 and Post-dredging: 306 ± 188; Table 4-3b). Mean population estimates for C2 were greatest during the Dredging Phase for both Marsh and Sinclair (1989) and Pollock et al. (2006) (Table 4-3b). However, in both estimation methods at all locations, there was considerable imprecision associated with the estimates as evident in the large overlapping SE values (Figure 4-7) suggesting that, while means varied, fluctuating values were still within the large margins of error. Furthermore, when comparing across surveys, due to low sighting numbers (i.e. ≤ 5 dugongs), population estimates may be based on only one replicate (see Table 4-3b), potentially introducing inaccuracy due to low replication.



Table 4-3 Comparison of dugong population estimates (±SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B3, D4 and P2; and b) across Baseline, Dredging and Post-dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006)

a) B3 D4 P2

Estimation Method Block Estimate ± SE n Estimate ± SE n Estimate ± SE n

Marsh and Sinclair C1 157 112 2 181 84 1 123 59 1

IM 401 167 3 382 154 3 306 188 3

C2 218 119 2 260 121 2 138 78 2

Pollock et al. C1 95 43 2 62 27 1 61 20 1

IM 268 128 3 193 59 3 187 104 3

C2 119 48 2 149 56 2 102 47 2

b) Baseline Phase Dredging Phase Post-dredging Phase



IM 359 154 7 305 173 9 306 188 3

C2 227 109 5 251 172 5 139 78 2

Pollock et al. C1 167 168 5 93 44 4 61 20 1

IM 231 138 7 180 80 9 187 104 3

C2 148 105 5 182 128 5 102 47 2



Mean population estimates and raw sighting numbers (±SE) for dugongs in each block Figure 4-7

during the TDMP from B1 (May 2012) to P2 (October 2014), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings data

N.B. Population estimates were not calculated for P1 (July 2014), only raw sightings are presented, refer to Section 4.1.1

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c) Raw sightings

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4.1.2.4 Dugong Densities – Whole Block As with the population size estimates (Section 4.1.2.3), the density of dugongs per km2 was not estimated for P1 (refer to Section 4.1.1). Density per km2 was calculated for all replicate flights for all survey blocks (C1, IM and C2) during P2 based on Marsh and Sinclair (1989) and Pollock et al. (2006) methods and raw sightings (Figure 4-8).

Based on raw sightings, the mean density of dugongs in P2 was 0.02 ± 0.01 per km2 for C1, 0.03 ± 0.01 per km2 for C2 and 0.08 ± 0.03 per km2 for IM (Figure 4-8c). The estimated mean density (±SE) of dugongs in C1 was 0.18 ± 0.09 per km2 based on the Marsh and Sinclair (1989) method and 0.09 ± 0.03 per km2 based on Pollock et al. (2006) method (Figure 4-8a, b). In the IM block, the estimated mean density of dugongs was calculated to be 0.30 ± 0.06 per km2 based on the Marsh and Sinclair (1989) method and 0.18 ± 0.03 per km2 based on Pollock et al. (2006) method, whereas in the C2 block, densities were 0.14 ± 0.04 dugongs per km2 and 0.10 ± 0.03 dugongs per km2 based on the two methods respectively.

Based on Marsh and Sinclair (1989), the estimated mean population density has shown considerable temporal variation across all blocks of the survey area. For IM, C1 and C2 blocks, P2 mean densities of dugongs were comparable to surveys carried out at similar temporal periods of B3 (C1: 0.19 ± 0.07; C2: 0.21 ± 0.04; IM: 0.35 ± 0.05) and D4 (C1: 0.26 ± 0.12; C2: 0.27 ± 0.07; IM: 0.37 ± 0.05). Due to limited sightings in C1 during D2, no estimates were calculated for this survey (Figure 4-8a).

During the TDMP, the IM block showed consistency in dugong density across the Baseline, Dredging and Post-dredging Phases (0.31 ± 0.02, 0.29 ± 0.02 and 0.30 ± 0.06 per km2 respectively) based on Marsh and Sinclair (1989) estimates. Similarly, C1 and C2 densities were also generally consistent across Phases with a small decrease observed in C2 during the Post-dredging Phase. Densities for C1 and C2 respectively, based on Marsh and Sinclair (1989), were 0.23 ± 0.02 and 0.22 ± 0.01 per km2 in the Baseline Phase, 0.24 ± 0.02 and 0.25 ± and 0.03 per km2 during the Dredging Phase and 0.18 ± 0.09 and 0.14 ± 0.04 per km2 during the Post-dredging Phase. However, notable decreases in dugong density were also observed, with the greatest evident during D2 (May 2013) across all sites (C2 and IM: 0.09 ± 0.04 per km2; C1 had too few sightings to derive an estimate).

The densities of dugongs per km2 based on Marsh and Sinclair (1989) and Pollock et al. (2006) estimation methods and raw counts for each replicate flight and survey period within each of the three blocks are presented in Appendix E.



Mean dugong density per km2 (±SE) in each block during the TDMP from B1 (May 2012) to Figure 4-8

P2 (October 2014), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings

N.B. Densities derived from population estimates were not calculated for P1 (July 2014), only densities from raw sightings are presented, refer to Section 4.1.1

Survey

Mea

n nu

mbe

r of i

ndiv

idua

ls p

er k

m-2

0.00

0.05

0.10

0.15

B1May 2012

B2July 2012

B3Oct 2012

D2May 2013

D3July 2013

D4Oct 2013

D5May 2014

P1July 2014

P2Oct 2014

c) Raw density

0.0

0.2

0.4

0.6

0.8 b) Pollock et al.

0.0

0.2

0.4

0.6

0.8 a) Marsh and Sinclair C1C2IM



Significant differences in dugong density estimates derived using the Marsh and Sinclair (1989) method were detected between Control and Impact Treatments (p < 0.05) and among Surveys within each Phase (all blocks combined, p < 0.05), while no other terms in the analysis were significant (Table 4-4a). Specifically, dugong density was lower in Control blocks (C1 and C2) compared to the Impact block regardless of Phase (Figure 4-9). Pairwise comparisons indicated that within the Dredging Phase, estimated dugong density was significantly lower in D2 (May 2013) compared to D4 (October 2013) (Figure 4-10). It is worth noting that no estimates were calculated for C1 and only one replicate flight was possible for each of C2 and IM blocks during D2 due to low sightings of dugongs.

Analyses of dugong density estimates derived using the Marsh and Sinclair (1989), Pollock et al. (2006) methods and raw sightings (Table 4-4) found no significant Phase x Treatment interaction, indicating that mean density did not significantly differ between Impact and Control Treatments during either Phase, or between Baseline and Dredging Phases for either Treatment.

Mean dugong population density estimates for all Phases combined calculated using the Figure 4-9

Marsh and Sinclair (1989) method at Control and Impact treatments

Dugong population density, averaged over all blocks, using the Marsh and Sinclair (1989) Figure 4-10method

4.1.2.5 Dugong Sub-block Population Estimates and Densities Sub-block estimates and densities were not calculated for P2 aerial surveys as there were too few sightings to compare across sub-blocks and would not provide accurate estimates of population size or reduce the variance (refer to Figure 4-1 for context).

0.0

0.1

0.2

0.3

0.4

Control Impact

Num

ber o

f ind

ivid

uals

km

-2

Treatment

0.0

0.1

0.2

0.3

0.4

B1May 2012

B2July 2012

B3Oct 2012

D2May 2013

D3July 2013

D4Oct 2013

D5May 2014

P1July 2014

P2Oct 2014

Num

ber o

f ind

ivid

uals

km

-2

Survey



Table 4-4 Results of univariate PERMANOVA tests for differences in the density of dugongs per km2 based on: a) the Marsh and Sinclair (1989) method; b) the Pollock et al. (2006) method; and c) raw sightings between three Phases (Baseline, Dredging and Post Dredging), including Phase (B1, B2 and B3 within Baseline Phase; D2, D3, D4 and D5 within Dredging Phase; and P1 and P2 within the Post-dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact)

N.B. P1 data is not included in the analysis of density of dugongs based on the Marsh and Sinclair (1989) and the Pollock et al. (2006) method (refer to Section 4.1.1)

Source of Variation (a) Marsh and Sinclair (1989) (b) Pollock et al. (2006) (c) Raw sightings

df MS Pseu-F p-(perm) df MS Pseu-F p-(perm) df MS Pseu-F p-(perm)

Phase 2 0.0046 0.29 0.8990 2 0.0151 0.54 0.7265 2 0.0018 0.73 0.6425

Treatment 1 0.0396 9.11 0.0170 1 0.0095 1.60 0.3176 1 0.0029 0.56 0.7265

Survey(Phase) 5 0.0257 18.18 0.0186 5 0.0257 3.64 0.2272 6 0.0017 0.87 0.5634

Block(Treatment) 1 0.0000 0.01 0.9139 1 0.0000 0.00 0.9848 1 0.0059 2.98 0.1341

Phase x Treatment 2 0.0049 1.26 0.3945 2 0.0061 0.54 0.7336 2 0.0010 0.48 0.8183

Phase x Block (Treatment) 2 0.0019 0.77 0.5375 2 0.0125 1.90 0.3009 2 0.0034 1.74 0.2489

Treatment x Survey(Phase) 5 0.0042 3.78 0.1426 5 0.0111 1.61 0.4197 6 0.0028 1.41 0.3583

Survey(Phase) x Block (Treatment) 3 0.0014 0.09 0.9644 3 0.0066 1.05 0.3709 6 0.0019 2.03 0.0786

Residual/Pooled residual 19 0.0146 19 0.0063 49 0.0010

Total 40 40 75

Pairwise Comparisons Impact > Control

(ranked from largest to smallest) Within Baseline: B2 = B3 = B1

Within Dredging: D4 > D2; all other comparisons not significant



4.1.3 Turtles

4.1.3.1 Sightings and Distribution

During P2 (October 2014), 987 turtles in total were sighted across all three blocks (C1: 320, 3 Reps; IM: 328, 3 Reps; C2: 339, 3 Reps). Most sightings were of individual turtles, while groups of two or more turtles were recorded sporadically (Appendix F). The total number of turtles sighted during P2 was higher than Baseline and Dredging Phase surveys, with B3 (October 2012), D5 (May 2014) and D4 (October 2013) observing 984 (9 Reps), 827 (8 Reps) and 813 (9 Reps) turtles respectively. The lowest number of turtles was recorded in B1 (May 2012) where 334 turtles were sighted, although only six replicate flights were flown during this survey (two in each block).

Turtle sightings during P2 occurred within each of the three survey blocks, consistent with all previous surveys. High concentrations of turtles were observed in shallow waters around the islands to the north-west of Bynoe Harbour in C1, between East Point and Lee Point and near Gunn Point in the IM block, and near the Vernon Islands in C2 (Figure 4-11). Comparatively, turtle sightings were generally sporadic through the deeper waters of Darwin Outer in IM, and in the channels adjacent to the islands in both C1 and C2 blocks, as has been observed in surveys across all Phases of the monitoring program.

The highest relative densities of turtle sightings per square kilometre in the IM block during the P2 survey were recorded in Darwin Outer around Gunn Point (grid cells 8, 16 and 24 with 4.26, 12.91 and 4.14 turtles per km2 respectively), between East Point and Lee Point (grid cells 19, 20 and 21 with 3.06, 3.35 and 5.5 turtles per km2 respectively), and along the north-eastern edge of Cox Peninsular (grid cell 43 and 17 with 6.04 and 4.85 turtles per km2 respectively) (Figure 4-12). Relatively high densities were also observed in Darwin Harbour Inner in Middle Arm and near Weed Reef during P2 (grid cells 31, 35 and 38 with 2.78, 2.49 and 3.98 turtles per km2 respectively). Similar densities were also observed during the B1 (May 2012) and D2 (May 2013), with maximum grid cell densities ranging between 2.51 per km2 (B1) and 4.67 per km2 (D2). Comparatively, densities observed during the remaining Dredging Phase surveys were slightly lower, with maximum grid cell densities ranging between 0.19 per km2 (D3) and 2.51 per km2 in (D5).

The spatial distribution of areas of high and low turtle density was found to be comparable to previously reported density patterns during the Baseline and Dredging Phase surveys. During P2, turtle density increased by more than 0.2 turtles per km2 in 23% of IM grid cells since B3, and decreased by more than 0.2 turtles per km2 in 56% of IM grid cells. A relatively small change in turtle densities (between -0.2 and 0.2 turtles per km2) from the B3 survey to P2 was observed in 21% of the IM grid cells (Figure 4-13). When comparing P2 to D4, the density of turtles per km2 in the IM block increased by more than 0.2 turtles in 54% of the grid cells, and decreased by more than 0.2 turtles per km2 in 19% of grid cells (Figure 4-14), with only a relatively small change (between -0.2 and 0.2 turtles per km2) detected for 28% of IM grid cells. Since D4, there was also an overall increase in 79% of IM grid cells in Darwin Harbour Inner and 48% of IM grid cells in Darwin Outer.



Distribution of turtles (based on raw sightings) during the P2 (October 2014) aerial surveyFigure 4-11



Density of turtle sightings (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM during the P2 Figure 4-12(October 2014) aerial survey



Relative difference in turtle density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM during Figure 4-13the P2 (October 2014) aerial survey compared to B3 (October 2012)



Relative difference in the turtle density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM Figure 4-14

during the P2 (October 2014) aerial survey compared to D4 (October 2013)



4.1.3.2 Turtle Bathymetric Distribution and Habitat Associations The depth distribution of turtle sightings during P2 varied between blocks, but was generally consistent across previous surveys undertaken during the monitoring program. Turtles were sighted across all depths during P2 (October 2014), with the majority of sightings (79%) occurring in waters less than -11 m LAT. Turtles in the deepest waters were sighted in C2 in waters up to -47.2 m LAT (Figure 4-15). For total numbers of turtles sighted in each block and survey, refer to Appendix F.

During P2, the majority of turtles were observed in waters up to -5 m LAT (58%), followed by 21% of sightings in the -6 m to -10 m LAT depth category, 16% in the -11 m to -20 m LAT depth category and a combined 5% of sightings in depths greater than -20 m LAT. In C1 and IM, the number of turtle sightings generally decreased with increasing depth, consistent with Baseline and Dredging Phase surveys.

In C1, the majority of turtles sighted during P2 (85%) occurred in waters up to -5 m LAT, with 13% and 3% in the -6 m to -10 m LAT and -11 m to -20 m LAT depth categories respectively. The pattern observed in IM was more gradual, with 63% of sightings in waters ≤ -5 m LAT, followed by 25%, 9% and 2% in the -6 m to -10 m LAT, -11 m to -20 m LAT and -21 m to -30 m LAT depth categories respectively. In contrast, the majority of sightings in C2 (36%) occurred in waters between -11 m and -20 m LAT. With a number of sightings also made in shallower depths, with 27% and 25% of sightings occurring in the 0 m to -5 m LAT and -6 m to -10 m LAT depth categories respectively and fewer sightings at depths greater than -20 m LAT (11%). Sightings across all blocks, while varying from each other, generally showed a consistent pattern of depth distribution across Baseline and Dredging Phase surveys.

During P2, the majority of turtle sightings occurred over gravel, sand and reef habitats comprising 35%, 31% and 20% of sightings respectively (Figure 4-16). Few turtles were sighted in association with other habitats, with less than 5% combined sighted over mangrove, seagrass, mud and rock habitats, and 10% sighted over unsurveyed habitat. In the C1 block, gravel and sand substrates accounted for 60% and 38% of all sightings, with few sightings occurring over mangrove and rock habitat (2% and 1% respectively). In IM, turtles were most frequently sighted over sand (46%), reef (31%) and gravel (21%) habitats. In C2, sightings were made across all habitat types except seagrass and rock, with the majority occurring over reef, unsurveyed habitat and gravel (32%, 29% and 26% respectively). Proportionally fewer sightings were made over sand (7%), mud (5%) and mangrove (<1%) habitats. While the turtle habitat associations varied somewhat between blocks, they were generally consistent across Baseline and Dredging Phase surveys.



Proportion of turtle sightings observed within different depth ranges (m) below LAT in: a) Figure 4-15C1; b) IM; and c) C2 for B1 (May 2012) to P2 (October 2014) aerial surveys


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 a) C1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Prop

ortio

n of

turt

le s

ight

ings

B1B2B3D2D3D4D5P2

b) IM

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 - 5 6 - 10 11 - 20 21 - 30 ≥ 31 Depth (m)

c) C2



Proportion of turtle sightings observed with respect to benthic habitat types at: a) C1; b) Figure 4-16IM; and c) C2 for B1 (May 2012) to P2 (October 2014)


00.10.20.30.40.50.60.70.80.9

1 a) C1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Prop

ortio

n of

turt

le s

ight

ings

b) IM B1B2B3D2D3D4D5P2

00.10.20.30.40.50.60.70.80.9

1

Benthic habitat type

c) C2



4.1.3.3 Turtle Population Size – Whole Blocks: Raw Sightings and Population Estimates Raw sightings for P1 are provided for context only in Figure 4-17c, noting data was considered unsuitable due to challenging conditions experienced during this survey (refer to Section 4.1.1). During P2, the mean numbers of turtles sighted for each block were C1: 106.7 ± 26.9, IM: 109.3 ± 26.8 and C2: 113.0 ± 13.5 (n = 3 flights within each block; Figure 4-17c).

Mean numbers of raw turtle sightings across the Baseline Phase varied greatly at all blocks. For IM, mean sightings were consistent throughout B1 and B2 (66.0 ± 10.0 and 68.7 ± 8.5, respectively), followed by an increase during B3 (116.3 ± 32.9). A similar trend was evident in C2 with B1 and B2 mean sightings being comparable (75.0 ± 13.0 and 64.0 ± 7.6 respectively) and B3 (117.7 ± 28.9) being higher (Figure 4-17c). However at C1, the initial survey (B1: 26.0 ± 1.0 SE) recorded the lowest mean number of sightings of the Baseline Phase surveys at all blocks, followed by an increase over the subsequent Baseline Phase surveys (up to 94.0 ± 7.5 during B3). Mean numbers of turtles observed during Dredging Phase surveys were similarly variable at C1 and C2, while at IM they were generally consistent, ranging between 53.7 ± 2.0 turtles (D3) and 83.3 ± 7.2 (D4). A decrease was observed during D2 at all blocks (following B3) which was particularly evident at IM (62.7 ± 11.0) and C2 (83.0 ± 22.0); however the mean numbers of turtles observed were comparable to previous Baseline Phase surveys (B1 and B2 ). At C1, sightings during D2 (91.0 ± 17.5) were comparable to B3, while D5 returned the highest mean number of sightings for this block (111.3 ± 9.0). Comparatively at C2, mean numbers of sightings increased during D4 and D5 (124.7 ± 14.0 and 150.5 ± 14.5 respectively). This increasing trend observed at C2 during the Dredging Phase was followed by a decrease in P2 (113.0 ± 13.5). Mean sightings in C1 and IM during P2 (106.7 ± 26.9 and 109.3 ± 26.8 respectively) were the second highest for their respective blocks compared to all other surveys throughout the TDMP. Overall, raw sightings indicate that, while mean numbers of turtles have been highly variable at all blocks over the duration of the monitoring program, Dredging and Post-dredging Phase sighting numbers are generally consistent with Baseline Phase levels for C1 and IM. Although mean sightings of turtles at C2 decreased from B3 to D3, there appears to be an increasing trend in turtles sighted at C2, with numbers during D4, D5 and P2 being consistently higher than Baseline Phase sightings.

Based on these raw sightings, population estimates were derived using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods. Mean group sizes and correction factors used for estimating turtle population size in aerial survey blocks C1, C2 and IM during P2 are presented in Table 4-5. As discussed in Section 4.1.1, turtle sighting data from P1 (July 2014) was not used to estimate population sizes for this time period. The PCFs and CVs calculated for turtle population size estimations during P2 ranged from 1.17 ± 0.03 for C2 to 1.38 ± 0.06 for the C1 block for starboard side observations, and from 1.25 ± 0.03 for C2 to 1.34 ± 0.05 for C1 for the port side observations. The PCFs were generally lower than those calculated for the Baseline and Dredging Phases, particularly for the starboard side (Cardno 2013a, 2014c), mainly as a result of increased recaptures between observers during P2 (between 29% and 48%; Table 4-6).



Mean population estimates and raw sighting numbers (±SE) for turtles in each block Figure 4-17during the TDMP from B1 (May 2012) to P2 (October 2014), based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) population estimate methodologies; and c) raw sightings data

N.B. Population estimates were not calculated for P1 (July 2014), only raw sightings data are presented, refer to Section 4.1.1

Survey

Mea

n nu

mbe

r of i

ndiv

idua

ls

0

50

100

150

200

250

B1May 2012

B2July 2012

B3Oct 2012

D2May 2013

D3July 2013

D4Oct 2013

D5May 2014

P1July 2014

P2Oct 2014

c) Raw sightings

0

500

1000

1500

2000

2500

3000 b) Pollock et al.

0

500

1000

1500

2000

2500 a) Marsh and Sinclair C1

C2

IM



Table 4-5 Details of turtle group size estimates for whole blocks and correction factors used in population estimates for the P2 aerial surveys The following parameters were used in the Marsh and Sinclair (1989) population estimate methods only: PCF – Perception Correction Factor; CV – Coefficient of Variation. Parameter estimates were based upon all sightings in the ‘inside’ and ‘outside’ zones

Survey Block Replicate Mean group size (CV) PCF (CV)

Starboard Port

P2

C1

1 1.07 (0.04)

1.38 (0.06) 1.34 (0.05) 2 1.29 (0.08)

3 1.14 (0.03)

IM

1 1.04 (0.02)

1.21 (0.03) 1.29 (0.04) 2 1.05 (0.02)

3 1.10 (0.04)

C2

1 1.04 (0.03)

1.17 (0.03) 1.25 (0.03) 2 1.07 (0.02)

3 1.07 (0.03)

Table 4-6 Sighting histories for turtles sighted during P2 aerial surveys by individual observers for each replicate flight, and all flights combined*

Block Rep Number of turtle groups seen by: # turtles sighted/ replicate

Total # turtle groups sighted

% turtle groups sighted by both observers

PF PR PB SF SR SB Port Starboard

C1

1 9 11 13 6 10 5 58 54 39% 24%

2 24 13 19 12 10 12 111 90 34% 35%

3 19 34 22 24 16 18 151 133 29% 31%

IM

1 9 13 15 5 13 16 74 71 41% 47%

2 16 18 17 9 9 20 92 89 33% 53%

3 21 37 29 32 10 18 162 147 33% 30%

C2

1 24 13 26 6 9 14 94 92 41% 48%

2 18 14 23 12 28 37 139 132 42% 48%

3 12 32 20 13 12 11 106 100 31% 31%

Total 152 185 184 119 117 151 987 908 35% 39%

Starboard front (SF); starboard rear (SR); starboard both (SB); port front (PF); port rear (PR) and port both (PB) * Replicates combined per block were used for population estimates and MARK analysis for the P2 survey



Due to the high number of turtle sightings across all surveys for all Phases (Baseline, Dredging and Post-dredging), there were sufficient data available to allow population sizes to be estimated for all blocks for all replicate flights. The mean population sizes for turtles during P2, derived using the Marsh and Sinclair (1989) method were estimated to be 626 ± 194, 661 ± 195 and 684 ±160 for C1, IM and C2 respectively. Population estimates derived using the Pollock et al. (2006) method (C1: 1,286 ± 427, IM: 1,332 ± 412 and C2: 1,235 ± 258) were notably higher (Table 4-7a, Figure 4-17b, Appendix G).

Using the Marsh and Sinclair (1989) method, population estimates for turtles varied considerably, with differences between Phases seen mainly within the IM block between Post-dredging (661 ± 195) and Baseline Phases (1,061 ± 709; Table 4-7b, Figure 4-17a, Appendix G); although this difference appears to be driven by the large population estimates in B2. P2 estimates for the IM block derived from Marsh and Sinclair (1989) were comparable to corresponding aerial surveys conducted in B3 (868 ± 405) and D4 (644 ± 108) (Table 4-7a, Figure 4-17a, Appendix G). When comparing mean populations across all survey periods for IM, estimates were highest in B2 (1,469 ± 890) and lowest in D2 (412 ± 106).

Similarly for C1, estimates across similar time periods (B3, D4 and P2) were comparable with 562 ± 212 in D4 and 778 ± 165 in B3 based on Marsh and Sinclair (1989). When comparing mean populations across all survey periods for C1, estimates for B2 were the highest (1,333 ± 788) and B1 the lowest at 335 ± 52 (Appendix G). Comparisons for the C1 block between Phases showed the lowest estimates during the Post-dredging Phase (626 ± 194) and the highest during the Baseline Phase (875 ± 630; Table 4-7b).

For C2, estimates based on Marsh and Sinclair (1989) were generally consistent between Phases, ranging between 831 ± 295 in the Baseline Phase and 684 ± 160 in the Post-dredging Phase. P2 population estimates for C2 based on Marsh and Sinclair (1989) were comparable to previous surveys carried out at a similar time period (B3 and D4) with estimates of 803 ± 211 and 825 ± 149 respectively. Overall, the highest estimate for C2 was calculated for D5 (1,013 ± 162), while the lowest was for D3 (565 ± 160). For estimates made using the Pollock et al. (2006) method, turtle population sizes during P2 were approximately double those calculated using the Marsh and Sinclair (1989) method.

Mean estimates for C1 were 1,286 ± 427 based on Pollock et al. (2006), with corresponding population sizes at similar times of the year were lower at 766 ± 154 in B3 and 470 ± 197 in D4. These were comparable to estimates derived using Marsh and Sinclair (1989) for the same periods of time. Furthermore, mean estimates for C1 during B2 using the Pollock et al. (2006) method were the highest turtle population size estimates for C1, which follows the same trend shown with estimates derived from Marsh and Sinclair (1989) methods (Appendix G).

Like C1 block, IM block mean estimates during P2 derived using the Pollock et al. (2006) method (1,332 ± 412), were the highest when comparing across all Phases (Table 4-7b). However, temporal comparisons showed that the highest mean population size estimates for IM occurred in B2 (1,437 ± 1,104). It should be noted that there are substantial error margins for these estimates, particularly for both C1 and IM estimates during B2 (for both methods of estimation), indicating a high degree of variability in data and that the estimates may be imprecise.

Similar to C1 and IM blocks, C2 turtle estimates using the Pollock et al. (2006) method were considerably higher compared to Marsh and Sinclair (1989) method estimates for P2 at 1,235 ± 258. Furthermore, unlike Marsh and Sinclair (1989), the Pollock et al. (2006) estimates for C2 during P2 were the highest when compared to all other TDMP surveys for C2, with previous estimates ranging from 541 ± 142 for D3 to 1,030 ± 179 in D5 (Appendix G). Comparisons between Phases showed the highest population size estimates for Pollock et al. (2006) occurred during the Post-dredging Phase, followed by Baseline Phase (868 ± 485). Although estimates for C2 during D5 were the second highest of all TDMP surveys, overall population estimates for C2 were lower during the Dredging Phase (747 ± 254; Table 4-7b), although the large standard errors of all Phases should be noted.

Overall, mean turtle population sizes estimated during the Baseline Phase were the highest across all blocks using the Marsh and Sinclair (1989) method, whereas population sizes were highest for the Post-dredging Phase as estimated by the Pollock et al. (2006) method (Table 4-7b). This pattern was also apparent for the IM block in particular, with IM block mean population size estimate using the Marsh and Sinclair (1989) method during the Baseline Phase at 1,061 ± 709. In contrast, the IM block turtle population size estimated from the Pollock et al. (2006) method (1,332 ± 412) was the highest during the Post-dredging Phase. This difference was driven largely by the large population size estimates calculated for replicate flights 2 and 3 for



IM block. For the C1 and C2 blocks, mean estimates were highest during Post-dredging according to Pollock et al. (2006). Conversely, C1 and C2 mean estimates were the highest during Baseline Phase according to Marsh and Sinclair (1989) methods.

Table 4-7 Comparison of turtle population estimates (±SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B3 (October 2012), D4 (October 2013) and P2 (October 2014); and b) across the Baseline, Dredging and Post-dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006)

a)

B3 D4 P2



IM 868 405 3 644 108 3 661 195 3

C2 803 211 3 825 149 3 684 160 3

Pollock et al. C1 766 154 3 470 197 3 1,286 427 3

IM 854 419 3 586 115 3 1,332 412 3

C2 809 223 3 782 167 3 1,235 258 3

b) Baseline Phase Dredging Phase Post-dredging Phase



IM 1,061 709 8 538 173 12 661 195 3

C2 831 295 8 745 243 10 684 160 3

Pollock et al. C1 874 730 8 643 237 12 1,286 427 3

IM 1,047 851 8 520 148 12 1,332 412 3

C2 868 485 8 747 254 10 1,235 258 3

4.1.3.4 Turtle Densities – Whole Blocks As for the population size estimates (Section 4.1.3.3), the density of turtles per km2 was not estimated for replicate flights during P1. For P2, the density of turtles per km2 was estimated for each of the replicate flights at C1, IM and C2. Based on Marsh and Sinclair (1989) methods, estimated mean density of turtles in the IM block was 0.64 ± 0.03 per km2. For C1 and C2, the estimated mean density (± SE) of turtles was 0.91 ± 0.05 per km2 and 0.70 ± 0.03 per km2 respectively (Figure 4-18a). Density estimates for turtles based on Pollock et al (2006) were notably higher for all blocks than Marsh and Sinclair (1989) (Figure 4-18b). Based on raw sightings in P2, the mean density of turtles was very similar in the IM and C2 blocks (0.53 ± 0.13 per km2 and 0.57 ± 0.07 per km2 respectively). For C1, density was higher 0.77 ± 0.19 turtles per km2.

Based on the Marsh and Sinclair (1989) method, turtle densities have shown some temporal and spatial variation in all blocks throughout Baseline, Dredging and Post-dredging Phases (Figure 4-18a). For IM, estimated densities were highest during B2 (July 2012; 1.26 ± 0.11), but were lowest during D2 (May 2013; 0.36 ± 0.02) and were generally lower throughout the monitoring program when compared to C1 and C2 blocks (Figure 4-18a). For Control locations, turtle densities in C1 were generally higher than those for C2 and had minimal fluctuations with the exception of B2. Estimated densities for C1 were generally comparable between Dredge Phase and Post Dredge Phase (P2) throughout all TDMP surveys, with the lowest densities seen during B1 (May 2012; 0.42 ± 0.03) and the highest during Baseline 2 (July 2012; 1.57 ± 0.08) (Figure 4-18a). For C2, estimated densities varied temporally with D5 recording the highest estimated densities (1.04 ±



0.06) and D3 the lowest (0.58 ± 0.04). Density estimates for the corresponding time periods to P2 (B3 and D4) showed B3 (October 2012) (0.76 ± 0.04) as being the highest.

For estimates based on Pollock et al. (2006) (Figure 4-18b), highest densities for the IM and C1 blocks were recorded during B2 (1.29 ± 0.06 and 1.87 ± 0.10 respectively). Overall, density estimates based on Pollock et al (2006) for IM were lower throughout the monitoring program than those for Marsh and Sinclair (1989) and the lowest during D2 (0.38 ± 0.03). Similar to Marsh and Sinclair (1989), C1 density estimates based on Pollock et al (2006) during B1 (May 2012) with the lowest densities across all TDMP surveys at 0.44 ± 0.14. Furthermore, an increase was evident from B1 (May 2012) to B2 (July 2012) with 0.62 ± 0.2 and 1.23 ± 0.20 respectively. Generally, estimated turtle densities were lower during the Dredging Phase compared to the Baseline Phase; however increased substantially during the Post-dredging Phase (Figure 4-18b). Based on raw sightings (Figure 4-18c), again turtle densities indicated some temporal and spatial variation within all blocks throughout he monitoring program. D5 had the highest turtle densities throughout the monitoring program for C1 and C2, whereas the highest densities for the IM block were recorded in B3. In general, the IM block had lower densities compared to both Control locations.



Mean turtle density per km2 (±SE) in each block during the TDMP from B1 (May 2012) to Figure 4-18P2 (October 2014), based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings data

N.B. Densities derived from population estimates were not calculated for P1 (July 2014), only densities from raw sightings are presented, refer to Section 4.1.1

Survey

Mea

n nu

mbe

r of i

ndiv

idua

ls p

er k

m-2

0.0

0.5

1.0

1.5

2.0

2.5 b) Pollock et al.

0.0

0.2

0.4

0.6

0.8

1.0

B1May 2012

B2July 2012

B3Oct 2012

D2May 2013

D3July 2013

D4Oct 2013

D5May 2014

P1July 2014

P2Oct 2014

c) Raw sightings

0.0

0.5

1.0

1.5

2.0 a) Marsh and Sinclair C1C2IM



Analysis of turtle density data derived using the Marsh and Sinclair (1989) method found a significant Phase x Treatment interaction (Table 4-8a). This indicates that differences in mean density between Impact and Control Treatments were dependent on Phase (i.e. Baseline and Dredging) and vice versa (Table 4-8a). Subsequent pairwise comparisons carried out to further examine this interaction indicated that there were lower densities in the IM block during the Dredging Phase and overall lower densities in the Control blocks across the whole survey period (Figure 4-19). Despite this, pairwise tests did not find any statistically significant differences (Table 4-8a).

Analysis of turtle density data derived using the Pollock et al. (2006) method and raw counts did not find a significant Phase x Treatment interaction (Table 4-8b, c). The only significant factors were Block, for the Pollock et al. (2006) method, and Treatment and the Survey x Block interaction for density calculated using raw counts (Table 4-8b, c). Pairwise comparisons for the Block factor indicated that turtle population density calculated with the Pollock et al. (2006) method was significantly higher in C1 block compared to the C2 block during the entire monitoring period (Table 4-8b, Figure 4-20). Pairwise comparisons for the Treatment factor of turtle densities calculated using raw sightings indicated that turtle density was higher in the Control treatment (C1 and C2 blocks combined) compared to the Impact block during the monitoring period (Table 4-8b, Figure 4-21). Comparisons between surveys within each Block for the interaction term Survey x Block indicated that there was a significant temporal variability within C1, C2 and IM blocks in the density of turtles calculated using raw counts, with six of the 30 pairwise tests being significant (Table 4-8c, Figure 4-18c). Pairwise comparisons between Blocks within the Control treatment (i.e. C1 and C2 blocks) for the interaction term Survey x Block indicated that C1 and C2 blocks were similar in all surveys with the exception of P1 when turtle density calculated using raw counts was higher in C2 than C1 (Table 4-8c, Figure 4-18c), noting this result should be treated with caution given the unfavourable weather conditions in P1 for aerial observations.



Table 4-8 Results of univariate PERMANOVA tests for differences in the density of turtles per km2 based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings between three Phases (Baseline, Dredging and Post Dredging), including Phase (B1, B2 and B3 within Baseline Phase; D2, D3, D4 and D5 within Dredging Phase; and P1 and P2 within the Post Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact)

N.B. P1 data is not included in the analyses of density of turtles based on the Marsh and Sinclair (1989) and the Pollock et al. (2006) method (refer to Section 4.1.1)

Source of Variation (a) Marsh and Sinclair (1989) (b) Pollock et al. (2006) (c) Raw sightings

df MS Pseudo-F p-(perm) df MS Pseudo-F p-(perm) df MS Pseudo-F p-(perm)

Phase 2 0.237 1.44 0.3342 2 3.59 1.71 0.2521 2 0.0444 0.89 0.5609

Treatment 1 0.369 1.46 0.3497 1 1.95 0.54 0.7183 1 0.5648 7.65 0.0211

Survey(Phase) 5 0.299 1.48 0.3447 5 0.30 2.06 0.3231 6 0.1126 0.91 0.5443

Block (Treatment) 1 0.326 1.59 0.2625 1 3.81 23.87 0.0322 1 0.0473 0.39 0.5557

Phase x Treatment 2 0.190 5.86 0.0236 2 0.51 0.34 0.9012 2 0.0875 1.77 0.2492

Phase x Block (Treatment) 2 0.002 0.04 0.9607 2 1.83 11.74 0.0569 2 0.0761 0.63 0.5675

Treatment x Survey(Phase) 5 0.062 0.33 0.8573 5 0.07 0.56 0.6076 6 0.0414 0.34 0.8924

Survey(Phase) x Block (Treatment) 5 0.198 1.30 0.2814 5 0.15 0.34 0.7762 6 0.1201 4.98 0.0005

Res 43 0.153 43 0.45 49 0.0241

Total 66 66 75

Pairwise Comparisons (ranked from largest to smallest)

Within Baseline: Control = Impact Within Dredging: Control = Impact Within Control: Baseline = Dredging Within Impact: Baseline = Dredging

Control 1 > Control 2

Control > Impact Within C1: B3 > B1; D5 > D3 Within C2: D5 = D4 > D3; P2 > P1 Within IM: D4 > D3 Within B1 to D5 and within P2: C1 = C2 Within P1: C2 > C1



Turtle population density calculated using the Marsh and Sinclair (1989) method at Figure 4-19Control and Impact treatments during Baseline, Dredging and Post-dredging Phases

Turtle population density calculated using the Pollock et al. (2006) method at Control (C1 Figure 4-20and C2) and Impact blocks (IM) across all surveys

Turtle population density calculated using raw sightings at Control (C1 and C2) and Figure 4-21Impact blocks (IM)

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4.1.3.5 Turtle Sub-block Population Estimates

During the P2 survey, turtle population estimates were calculated for each sub-block across each primary block (averaged across replicate flights ±SE), which are divided up based on areas with similar bottom type and bathymetry. Around Bynoe Harbour (C1), population estimates for the four sub-blocks ranged between 29 ±14 turtles in sub-block C-1 and 381 ± 130 for the western sub-block C1-2 based on the Marsh and Sinclair (1989) method. The Pollock et al. (2006) method had higher estimates, ranging from 68 ± 33 turtles in sub-block C1-1 to 832 ± 275 turtles in sub-block C1-2 (Table 4-9).

Within the six sub-blocks of the Darwin Harbour/Hope Inlet region (IM block), population estimates ranged from 28 ± 15 turtles in the offshore IM-6 sub-block, to 150 ± 23 turtles for sub-block IM-4 in Hope Inlet, using the Marsh and Sinclair (1989) method. The Pollock et al. (2006) method gave higher values, estimating between 64 ± 34 turtles ((IM-6), and 328 ± 176 turtles (IM-1), which comprises the inner waters of Darwin Harbour, in contrast to the Marsh and Sinclair (1989) estimate.

Around the Vernon Islands and up toward Melville Island (C2), population estimates within the four sub-blocks ranged from 75 ± 23 turtles in sub-block C2-4 to 296 ± 68 turtles for sub-block C2-2 in the shallow reef area surrounding the Vernon Islands using the Marsh and Sinclair (1989) method. The Pollock et al. (2006) method estimated between 147 ± 51 turtles for C2-4 and 508 ± 153 for C2-2 (Table 4-9, Appendix I).

When using the Marsh and Sinclair (1989) method, population estimates were highest overall in C1-2 and C2-2 (381 ± 130 and 296 ± 68 turtles respectively; Table 4-9), which corresponds with the islands in the northwest of Bynoe Harbour, and the shallow reef surrounding the Vernon Islands (Figure 4-11). Estimates were lowest in IM-6 and C1-1 (28 ± 15 and 29 ± 14 turtles respectively), corresponding to the outermost region of the IM block and the inner areas of Bynoe Harbour. When using the Pollock et al. (2006) method, the highest and lowest estimates were found in the same sub-blocks as those using the Marsh and Sinclair (1989) method; however these values were substantially higher (Table 4-9).

Table 4-9 Turtle population estimates (±SE) for each sub-block during P2 (October 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006), averaged across replicate flights

Marsh and Sinclair (1989) Pollock et al. (2006)

Block Sub-block n* Population Estimate ± SE Population

Estimate ± SE

C1

1 3 29 14 68 33

2 3 381 130 832 275

3 3 152 48 356 120

4 2 83 49 167 82

Total 645 148 1,437 302

IM

1 3 149 81 328 176

2 3 103 31 204 68

3 3 145 48 276 98

4 3 150 23 298 72

5 3 88 42 170 78

6 1 28 15 64 34

Total 663 111 1,340 240

C2

1 3 123 50 254 93

2 3 296 68 508 153

3 3 159 49 333 80

4 3 75 23 147 51

Total 653 100 1,242 203

* n = number of replicate flights where ≥1 turtle sighting was recorded.



4.1.3.6 Turtle Sub-block Densities

Turtle density estimates within each sub-block (number per km2 ± SE) were calculated by dividing the derived population estimates by the total transect area sampled over water within each sub-block. Estimates for the C1 sub-block densities in P2 ranged between 0.10 ± 0.05 turtles per km2 for C1-1 to 0.43 ± 0.11 turtles per km2 for C1-2, based on Marsh and Sinclair (1989), and between 0.24 ± 0.10 turtles per km2 and 0.94 ± 0.25 per km2 based on Pollock et al. (2006) (Table 4-10). Mean turtle density in IM sub-blocks ranged between 0.03 ± 0.01 turtles per km2 in the offshore IM-6 sub-block to 0.40 ± 0.13 turtles per km2 for IM-3, the sub-block encompassing the waters between Fannie Bay and Lee Point. The Pollock et al. (2006) method estimated between 0.06 ± 0.03 and 0.76 ± 0.25 turtles per km2 for IM-6 and IM-3 respectively. Within the C2 sub-blocks, the mean density ranged between 0.13 ± 0.03 turtles per km2 in the C2-3 sub-block, and 0.48 ± 0.11 turtles per km2 in C2-2 around the Vernon Islands. Using the Pollock et al. (2006) method, estimates were between 0.28 ± 0.07 and 0.82 ± 0.18 turtles per km2 for the same sub-blocks respectively (Table 4-10, Appendix J).

Similar to the population estimates, turtle densities in P2 were highest for both methods of estimation in the C2-2 and C1-2 sub-blocks, corresponding to the waters around the Vernon Islands and the islands in the north-west of Bynoe Harbour. While the Marsh and Sinclair (1989) method gave the highest estimated density in C2-2 of all sub-blocks, the Pollock et al. (2006) method gave the overall highest estimated density in C1-2. The areas with the lowest densities were IM-6 and C1-1, the outermost areas of the Darwin Harbour/Hope Inlet block and the inner areas of Bynoe Harbour.

Table 4-10 Turtle density estimates (per km2) for each sub-block during P2 (October 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006)


Block Sub-block Area (km²) Density Estimate ± SE Density

Estimate ± SE

C1

1 94.7 0.10 0.05 0.24 0.10

2 296.4 0.43 0.11 0.94 0.25

3 150.2 0.34 0.09 0.79 0.24

4 145.8 0.28 0.13 0.38 0.14

IM

1 193.8 0.26 0.05 0.56 0.15

2 128.7 0.27 0.08 0.53 0.17

3 121.5 0.40 0.13 0.76 0.25

4 171.5 0.29 0.05 0.58 0.15

5 85.9 0.34 0.09 0.66 0.21

6 333.1 0.03 0.01 0.06 0.03

C2

1 224.5 0.18 0.07 0.38 0.13

2 207.1 0.48 0.11 0.82 0.18

3 393.6 0.13 0.03 0.28 0.07

4 150.7 0.17 0.05 0.33 0.11

4.1.3.7 Turtle Whole Block vs Sub-block Population Estimates During P2, population estimates for turtles derived for each whole block were similar to estimates calculated for each of the sub-blocks using both estimation methods (Figure 4-22). Based on the Marsh and Sinclair (1989) method, mean turtle population size estimates (±SE) derived for sub-blocks were 645 ± 148 in C1, 663 ± 111 in IM and 653 ± 100 turtles in C2 (Table 4-9, Figure 4-22a). Using this method, estimates for both block and sub-block analyses were remarkably similar across all locations; however with the sub-block analysis, the level of error present was reduced compared with the whole blocks.

Using the Pollock et al. (2006) method, mean turtle population size estimates (±SE) derived for sub-blocks were 1,437 ± 302 in C1, 1,340 ± 240 in IM and 1,242 ± 203 in C2 (Table 4-9, Figure 4-22b). These sub-block population estimates for IM and C2 were similar to whole block estimates. However, sub-block population



estimates for C1 where higher than the whole block population estimate by 151 turtles. Similar to the Marsh and Sinclair (1989) method, margins of error were reduced when using the sub-block analysis compared with whole blocks.

Mean population estimates (±SE) for turtles derived from whole block and sub-block Figure 4-22

calculations based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) at each block for P2 (October 2014)

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4.2 Land-based Surveys

4.2.1 Survey Effort and Environmental Conditions

Land-based surveys for P2 (October 2014) were undertaken on two field days (14 October 2014 and 23 October 2014) from Channel Island Bridge and the rock wall at Cullen Bay. Average BSS and turbidity for each survey day at each location are presented in Table 4-11.

Survey days were undertaken during a falling and rising spring tide. The tidal changes over which sampling was conducted were between 1.3 m and 2.7 m on 14 October 2014 and 3.4 m and 4.5 m on 23 May 2014 (Table 4-11). Raw data for each land survey period undertaken during P2 are presented in Appendix K.

Table 4-11 Survey effort for land-based surveys during P2 (October 2014)

Date Location surveyed Tidal window (cm)

Survey start time

Average BSS

Average Turbidity

14 October 2014 Channel Island Bridge 575 – 371 7:40 1.6 4.0

14 October 2014 Cullen Bay 544 – 410 7:10 2.0 4.0

23 October 2014 Channel Island Bridge 493 – 154 7:50 1.6 3.0

23 October 2014 Cullen Bay 609 - 159 6:45 1.3 4.0

4.2.2 Channel Island Bridge

All sightings recorded at Channel Island Bridge during P2 (October 2014) were of turtles (128 sightings), with 88% of these identified as green turtles. The remaining 12% of sightings were unable to be identified to species level and are categorised as ‘unidentified’ turtles (Table 4-12, Figure 4-23). Juvenile turtles accounted for 82% of the recorded sightings, with 13% identified as adults. No dugongs were sighted during the P2 survey at Channel Island Bridge.

There were considerably more sightings made on Day 1 of the P2 survey, making up 73% of sightings at Channel Island Bridge. The number of sightings made during P2 was lower than D3 and D4 (291 and 194 sightings respectively; Table 4-13), although higher than D2 and D5 (115 and 61 sightings respectively). While the number of sightings made on Day 1 was comparable to previous Dredging Phase surveys, Day 2 of P2 returned the second lowest number of sightings from all land survey days (Day 2 of the D5 survey was the lowest, where just six sightings were recorded).

4.2.3 Cullen Bay Rock Wall

During P2, there were 16 sightings of marine megafauna recorded at Cullen Bay rock wall, with the majority (69%) recorded in the north eastern quadrant (Table 4-12, Figure 4-23). P2 had a moderate number of sightings, with higher numbers than D2 and D3 (2 and 7 sightings respectively; Table 4-13), although substantially lower sightings than D4 and D5 (51 and 54 sightings respectively). During P2, 75% of sightings at Cullen Bay rock wall were of dugongs, with the remainder of sightings made of dolphins. No turtles were sighted on either survey day at Cullen Bay rock wall during P2.

Twelve sightings were made of dugongs at Cullen Bay on Day 1 from both the western and north-eastern sides of the rock wall. Initial sightings were made on the western side over a period of 26 minutes, followed by sightings over 2 minutes where a dugong transited from the west to the north-eastern side, and finally sightings were made over a 10-minute period on the north-eastern side with the animal surfacing regularly. It is not possible to determine whether they were of the same individual; however, given the locations of the sightings were consistent with the patterns of movement exhibited, it is likely that all sightings were of the same dugong. During the TDMP, there have been regular sightings of dugongs at Cullen Bay during land observations (D3, n = 6; D4, n = 35 and D5, n = 5), often with individuals transiting through the survey area, potentially moving between foraging areas.



Table 4-12 Number of megafauna sightings and number of individual animals observed at Channel Island Bridge and Cullen Bay rock wall during P2 (October 2014) land-based surveys

Channel Island Bridge Day 1 Day 2

Total sightings Individuals* Total sightings Individuals*

Unidentified turtle 2 2 13 13

Green turtle 92 73 21 19

Dugong 0 0 0 0

Dolphin 0 0 0 0

Total sightings 94 75 34 32

Cullen Bay Rock Wall

Unidentified turtle 0 0 0 0

Green turtle 0 0 0 0

Dugong 12 3 0 0

Dolphin 1 1 3 1

Total sightings 13 4 3 1

* Individuals recognised through discernible features or observation of dive behaviour

Table 4-13 Total number of megafauna sightings observed at Channel Island Bridge and Cullen Bay rock wall during all Dredging (D2, D3, D4 and D5) and Post-dredging Phase (P2) land-based surveys N.B. Counts are of total sightings, not individuals. Land-based surveys were not undertaken during the Baseline Phase (2012) or during P1 (July 2014)

Channel Island Bridge D2 D3 D4 D5 P2

Day 1 Day 2 Day 1 Day 2 Day 1 Day 2 Day 1 Day 2 Day 1 Day 2

Unidentified turtle 41 27 14 0 10 69 10 5 2 13

Green turtle 25 13 98 179 71 13 45 1 92 21

Dugong 0 0 0 0 0 0 0 0 0 0

Dolphin 4 5 0 0 31 0 0 0 0 0

Total sightings 70 45 112 179 112 82 55 6 94 34 Cullen Bay Rock Wall

Unidentified turtle 0 1 0 0 0 4 0 0 0 0

Green turtle 1 0 0 0 0 7 0 0 0 0

Dugong 0 0 1 5 0 35 2 3 12 0

Dolphin 0 0 1 0 0 5 9 40 1 3

Total sightings 1 1 2 5 0 51 11 43 13 3 Maximum tidal movement (m) 2.1 5.1 1.6 1.3 0.7 4.5 3.8 5.2 2.7 4.5



Distribution of megafauna sighted during land-based surveys in P2 (October 2014) Figure 4-23N.B. Points indicate the initial sighting of an individual or group; multiple animals made during a single sighting are denoted by one dot as animals are recorded at the same location



4.3 QA/QC for Aerial and Land-based Surveys During P1, there were 304 line entries quality checked within the aerial survey observer database, with two errors detected (0.7%). As part of the environmental database quality control check, 227 line entries were checked, with no errors detected. During the master database quality check 609 entries were checked, with four errors identified (0.7%).

During P2, a total of 404 line entries were quality checked within the aerial survey observer database, with 13 errors detected (3.2%). As part of the environmental database quality control check, 189 line entries were checked, with one error detected (0.5%). During the master database quality check 1,091 entries were checked, with 18 errors identified (1.7%). All errors were subsequently corrected.

All sighting and environmental entries in the land-based survey observer database were checked against the datasheets for quality assurance and no errors were found.

4.4 Rehabilitated Turtles As of November 2014, species collected for rehabilitation have included two olive ridley, three green, four hawksbill and eight flatback turtles. A summary of all rehabilitated turtles (current and past) reported to Cardno by the Arafura Timor Research Facility or the DLRM since the commencement of the TDMP is provided in Appendix L. Only one of these rehabilitated turtles, named ‘Linh’, was found to be suitable for satellite tagging.

Linh is an adult female hawksbill turtle that was rescued from an illegal fishing vessel near Evans Shoal, 250 km north of Darwin by Australian Fisheries Management Authority (AFMA) in early March 2014. Linh was fitted with a satellite transmitter and flipper tag following rehabilitation and was released on 27 March 2014 by DLRM at Nightcliff Jetty, Darwin. Transmitted data showed that Linh initially went north-west, travelling up to 78 km from the release site but spent the majority of time in waters approximately 30 km offshore, north east of Darwin (Cardno 2014c). During the first month of tracking, Linh travelled a distance of approximately 214 km (Figure 4-24). The last recorded location for Linh occurred on 9 August 2014 at 0100 hours, 37.2 km north-west of Nightcliff Jetty (Figure 4-24). Satellite data for the ensuing weeks showed that Linh remained in this area until ARGOS satellite tracking ceased on 16 August 2014.

Of the Fastloc GPS location data recorded (n = 347), 74.6% (n = 259) occurred within the period 27 April 2014 to 9 August 2014. Of the location points recorded during this time period, 96.5% (n = 250) were within a defined area, approximately 30 km north-west of Nightcliff Jetty within an approximate 196 km2 area. The total distance travelled by Linh over the duration of the satellite tracking period and based on all Fastloc GPS location points was 515.7 km, with nearly 60% of this distance (301.7 km) recorded within an area of approximately 237.5 km2 since 27 April 2014 (Figure 4-24).

Over 135 days of tracking, 1,222 dives were recorded for Linh. Of these, only 908 dives were able to record dive duration information. The majority of Linh’s dives (49.5%) were recorded at depths within the 31 m to 40 m depth range (Figure 4-25). A total of 151 dives (12.4%) were recorded in the 26 m to 30 m depth category, with these dives occurring mainly within the second month of tracking. Most of Linh’s dives to depths greater than 40 m (31.5%) were recorded on a single day (27 April 2014) coinciding with Linh’s furthest Fastloc GPS position from the release site (recorded on 26 April 2014; Figure 4-24). The greatest number of shallow dives (0 m to 5 m) by Linh was carried out on the day she was released from Nightcliff Jetty on 27 March 2014 (36%).

The duration of dives made by Linh tended to be long, with 29.5% of the total 908 dives exceeding 60 minutes in duration (Figure 4-26), and a further 116 dives (12.8%) lasting for 31 to 40 minutes. Notwithstanding this, Linh also made a number of shorter dives (16.3%), between 0 and 5 minutes mainly during the first month of tracking, which corresponds with the shallower dive depths made during this period of time.



Transmitted geo-locations of ‘Linh’, between 27 March 2014 and 16 August 2014Figure 4-24



Proportion of dives at specific depths (m) for tagged rehabilitated turtle ‘Linh’ Figure 4-25

Proportion of dives for specific durations (min) for tagged rehabilitated turtle ‘Linh’ Figure 4-26

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5 Discussion

The TDMP has incorporated various visual survey techniques to estimate and monitor the abundance and distribution of turtles and dugongs within the Darwin region during the Baseline Phase (B1, May 2012; B2, July 2012; B3, October 2012), Dredging Phase (D2, May 2013; D3, July 2013; D4, October 2013) and Post-dredging Phase (P1, July 2014; P2, October 2014) of the Project EA and GEP dredging activities. Aerial surveys allowed relative abundances of turtles and dugongs to be compared between areas of Darwin Harbour, Hope Inlet and Shoal Bay (within IM block), Bynoe Harbour (C1 block) and waters between the mouth of the Adelaide River and Melville Island, including the Vernon Islands (C2 block). Turtles were also tagged to investigate their fine-scale movement, behaviour and habitat utilisation.

Post-dredging Phase survey P1 (July 2014) commenced approximately one month and one week after the completion of EA (11 June 2014) and GEP (12 July 2014) dredging operations respectively, while P2 (October 2014) commenced approximately four and three months after the completion of EA and GEP dredging operations respectively. These Post-dredging Phase surveys were designed to provide a means to investigate potential short- and medium-term changes in turtle and dugong populations and distributions around the Darwin region following the completion of Project dredging activities through the comparison of data collected during the Dredging and Baseline Phases. Due to the unfavourable weather conditions experienced during the P1 survey, (elevated BSS and high wind speeds, see Section 4.1.1), data collected during this aerial survey were determined to be unsuitable and were excluded from Post-dredging Phase (short-term) analysis (with only raw sighting data from the P1 survey included where appropriate).

5.1 Dugongs Throughout the TDMP, aerial surveys suggested some variation in the overall population estimates of dugongs among surveys. Data suggested that population estimates of dugongs fluctuated about a mean for all three blocks (C1, C2 and IM) and that there was no obvious trend (decline or increase) for any of the monitoring blocks. During the Post-dredging Phase, mean population estimates of dugongs within all three blocks ranged from 123 ± 59 (C1) to 306 ± 188 (IM) (as estimated using the Marsh and Sinclair (1989) method) or 61 ± 20 (C1) to 187 ±104 (IM) (as estimated using the Pollock et al. (2006) method). These ranges in mean population estimates were consistent with aerial survey data collected in the Baseline and Dredging Phases for comparable times of year (B3; October 2012 and D4; October 2013; Cardno 2014c). Throughout the TDMP, raw sightings and population estimates of dugongs in the IM block were generally greater than for the Control blocks. Similarly, the estimated population density of dugongs in the IM block, calculated using the Marsh and Sinclair (1989) method was significantly greater than for the Control blocks for all Phases (Baseline, Dredging and Post-dredging). These results provide no evidence to suggest Project dredging or spoil disposal activities affected dugong sightings, abundance estimates or densities within the Darwin region.

It is possible that higher numbers of dugongs observed in the IM block throughout the TDMP relative to the Control blocks was a consequence of various factors including the spatial distribution of seagrass habitat in the IM area (Cardno 2014d; GeoOceans 2014d), seagrass being a preferred food source for dugongs (Anderson 1998). As such, variability in seagrass spatial and temporal distribution may result in the temporary movement of dugongs in search of optimum foraging areas.

In support of this conclusion beds of Halophila and Halodule have been recorded in varying densities in the IM block, primarily at East Point, Fannie Bay, along Casuarina Beach and in waters surrounding Lee Point, throughout the Baseline, Dredging and Post-dredging Phases (Cardno 2014c,d; GeoOceans 2014d). During P2 (October 2014), seagrass surveys were also carried out which indicated that seagrass extent and density was greatest between East Point and Lee Point compared to other areas of mapped seagrass in the Darwin Outer region (Cardno 2014d), with an overlap observed between dugong sightings during P2 and mapped seagrass habitat. A similar pattern was also evident in previous surveys carried out in the late dry season during both the Baseline (B3) and Dredging (D4) Phases, where high dugong densities were associated with shallow seagrass habitats in the IM block. For each Phase of the TDMP, sightings and densities of dugongs in the IM block generally increased between the beginning and end of the dry season, when overall sighting



numbers were greatest. This was consistent with the seasonal increase in seagrass extent and density in IM over the corresponding periods (Cardno 2014d).

Very few dugongs were also sighted (in aerial, boat- or land-based surveys) in Darwin Harbour Inner during the TDMP (including in the Baseline Phase). As such, it appears that dugongs do not regularly frequent the Darwin Harbour Inner area.

5.2 Turtles During the TDMP, turtle sightings recorded during aerial surveys were an order of magnitude greater than for dugongs. During the Post-dredging Phase, population estimates of turtles based on the Marsh and Sinclair (1989) method ranged from 626 ± 194 (C1) to 684 ± 160 (C2), consistent with aerial survey data collected in the Baseline and Dredging Phases (Cardno 2014c). However, abundances in P2 (October 2014) based on the Pollock et al. (2006) method increased substantially from Baseline and Dredging Phase estimates, ranging from 1,235 ± 258 (C2) to 1,332 ± 412 (IM).

During P2, mean raw sightings of turtles in the IM block were similar to those seen in Control blocks (C1 and C2). In contrast, mean raw counts of turtles in the IM block during Baseline and Dredging Phases were generally less than the means seen in C1 and C2. It is unclear why less turtles were sighted in the IM block compared to the Control blocks; although as this result has been observed consistently throughout the TDMP, it does not indicate an effect of Project dredging activities. It is worth noting that in the final Post-dredging Phase survey (P2), raw sightings of turtles were similar for the three blocks and generally amongst the highest recorded for the entire TDMP, particularly for C1 and IM blocks.

The decrease in density of turtles (estimated using the Marsh and Sinclair (1989) method) for the IM block between Baseline and Dredging Phases (Cardno 2014c) was likely a result of the population estimate methodology, rather than reflecting any real change in the abundance of turtles in this area. Methods for estimating the size of populations are prone to large errors where there are low recapture rates (i.e. animals not recorded by both front and rear observers). During the B2 survey, the population estimate calculated for Rep 2 was substantially higher than all other replicates from the Baseline Phase and, in addition, there were unusually high PCFs for all blocks even though there were a smaller number of sightings for that particular survey (compared to subsequent surveys). Hence, as similarly high PCF values were not observed in other surveys, it is considered that the decrease in density of turtles for the IM block between Baseline and Dredging Phases was a result of population estimate methodology, rather than being an actual change in the abundance of turtles in the IM block.

In the Post-dredging Phase, as well as previous surveys in the TDMP, turtles were sighted in all sub-blocks of IM, C1 and C2, including Darwin Harbour Inner, where Project dredging and construction activities occurred. Densities were highest within sub-blocks C2-2 and C2-1, comprising the shallow reef areas around the Vernon Islands and islands to the north-west of Bynoe Harbour. Consistent with this, throughout the TDMP turtles were most frequently sighted in relatively shallow water habitats (0 m to -5 m LAT) over reef, sand and gravel at IM and over sand and gravel at C1, while in C2 most sightings occurred in depths of -11 m to -20 m LAT over reef, gravel and unsurveyed habitats. It is difficult to determine the reasons for varying turtle sightings between blocks, although it is likely due to a combination of factors, including the bathymetric characteristics and habitat types available in Darwin Harbour and the surrounding areas. Observers were unable to identify turtle species in aerial surveys, but given, for example, that green turtles prefer feeding on marine plants (Whiting 2000), which are found in shallow water, and flatback or hawksbill turtles feed largely on sponges or soft corals (NAILSMA 2006), which are generally found in deeper water, it is possible that varying densities of turtles in different areas within the blocks may be a reflection of available habitat and species specific optimum foraging conditions. Findings from land-based surveys and satellite tagged turtles further support this theory of species specific habitat preferences. That is, during land-based surveys turtles in the shallow waters around Channel Island Bridge were mostly identified as green turtles, while the four juvenile green turtles satellite tagged at Channel Island remained in the area (within core home ranges of up to 1.5 km2) and recorded dives mostly in a depth range of 0 m to -15 m LAT (Cardno 2014c). In contrast, the rehabilitated turtle Linh, a tagged adult hawksbill turtle released at Nightcliff Jetty, spent the majority of time in an area approximately 30 km offshore from her release site (within an area approximately 196 km2), regularly diving to depths of -31 m to -40 m LAT, which may likely be a reflection of foraging behaviour for deep water sponges, the known dietary preference for hawksbill turtles.



6 Conclusion

Aerial surveys undertaken throughout the Dredging Phase (D2: May 2013, D3: July 2013, D4: October 2013 and D5: May 2014) and Post-Dredging Phase (P1: July 2014 and P2: October 2014) demonstrated natural spatial and temporal variability in distribution and relative abundance of turtles and dugongs in the Darwin region and surrounding areas with no evidence to suggest any impact of Project activities. Land-based surveys, in combination with turtle tagging and satellite tracking provided fine-scale information on green turtle behaviour and movement around Channel Island Bridge, as well as the movements and behaviours of a tagged adult hawksbill approximately 30 km offshore from her release sight at Nightcliff jetty.

The few sightings of dugongs in Darwin Harbour Inner during the TDMP suggest that Darwin Harbour Inner is not an area regularly frequented by dugongs. Greater numbers of dugongs were sighted in Darwin Outer, most often within shallower waters (0 m to -10 m LAT). These sightings coincided with mapped seagrass (Halophila and Halodule) habitats at Casuarina Beach and Lee Point, suggesting the importance of these foraging grounds to dugongs. Despite fluctuations in the mean number of dugong sightings and substantial variability between replicate flights, there was no obvious spatial or temporal trend to indicate the number of dugongs have been affected by Project dredging activities. Given the association of dugongs with seagrass habitat, patterns in dugong distribution and abundance throughout the TDMP were considered to be the result of natural variation potentially driven by spatial and temporal variations in seagrass habitats (extent and density).

During the Post-dredging Phase, mean turtle densities were the generally highest across all blocks compared to the Baseline and Dredging Phases (based on the Pollock et al. (2006) method); although temporal and spatial variation was evident throughout the TDMP. The observed variability of turtle sightings among surveys and smaller-scale spatial patterns within the survey blocks was likely a result of seasonal movements and habitat preferences of the various species of turtles that occur in the Darwin region. There was no obvious trend in turtle abundance for any of the blocks that would potentially indicate a delayed effect of Project-related dredging activities and patterns in turtle distribution and abundance were considered to be the result of natural variation.

Land-based surveys were effective in determining the distribution and turtle species presence at Channel Island. Complimenting this was satellite tracking of turtles throughout the TDMP, which provided additional information on the habitat usage of juvenile green turtles at Channel Island. Given the four tagged juvenile green turtles remained within this area throughout the duration of satellite tracking, it is likely they also used these areas for foraging. Furthermore, these individuals seemed to remain within smaller core home ranges in shallow waters around Channel Island. The tagged adult hawksbill turtle released at Nightcliff Jetty also appeared to exhibit a core home range, but in contrast to the green turtles, remained in deeper water about 30 km from the shore.

In summary, the objectives of the TDMP have been met. There have been some fluctuations in the abundance and distribution of both turtles and dugongs throughout the Darwin region during the course of the TDMP; however, these are likely a result of natural variation in response to spatial and temporal variability in habitat and/or species preference. In addition, land-based surveys, in combination with turtle tagging and satellite tracking, successfully provided fine-scale information on the behaviour and habitat preferences of various turtle species. Based on this available evidence, there is no indication that Project dredging activities have had an impact on turtle or dugong abundance, distribution or the finer-scale aspects of their populations in the Darwin region.



7 Acknowledgements

This report was written by Ivon Sebastian, Freya Muller and Dr Andrea Nicastro, and reviewed by Dr Craig Blount, Dr Michelle Blewitt and Dr Lachlan Barnes. GIS support was provided by Shani Archer. Data analysis and figure, table and appendix preparation was undertaken by Freya Muller, Dr Andrea Nicastro and Ivon Sebastian.

Fieldwork for the P1 and P2 surveys was undertaken by Dr David Waayers, Dr Glenn Dunshea, Barry Krueger, Paul Tod, Freya Muller, Megan Ridgway and Dr Andrea Nicastro.

Logistical and communications support during P1 and P2 field sampling was provided by Erica Griffiths from Sydney, Todd Sinclair in the Cardno office in Darwin, and Skye Stevens based in Perth.



8 References Anderson, P.K. (1981). The behaviour of the dugong (Dugong dugon) in relation to conservation and management. Bulletin of Marine Science, 31, pp. 640-647.

Anderson, P.K. (1998). Shark Bay dugongs (Dugong dugon) in summer. II: Foragers in a Halodule-dominated Community. Mammalia. 62(3):409-425.

Anderson, M.J. (2001). A new method for non-parametric multivariate analysis of variance. Austral Ecology, 26, pp. 32-46.

Australian Hydrographic Service (2003). AUS 26 − Approaches to Port Darwin.

Australian Hydrographic Service (2007). AUS 24 − Port Darwin Wickham Point.

Australian Hydrographic Service (2009a). AUS 27 − Port Darwin Middle Arm - Including Channel Island.

Australian Hydrographic Service (2009b). AUS 28 − Port Darwin East Arm.

Cardno (2013a). Turtle and Dugong Monitoring Program Baseline Report. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013b). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 1. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013c). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 2. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013d). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 3. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2014a). Nearshore Environmental Monitoring Plan (Rev. 5). Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2014b). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 4. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2014c). Routine Turtle and Dugong Monitoring Program Report – End of Dredging Report . Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney

Cardno (2014d). Seagrass Monitoring End of Dredging Report. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Chatto R. and Baker B. (2008). The distribution and status of marine turtle nesting in the Northern Territory, Technical Report 77/2008, Prepared for Parks and Wildlife Services, Northern Territory.

Costa, D.P., Robinson, P.W., Arnould, J.P.Y., Harrison, A.-L., Simmons, S.E. (2010). Accuracy of ARGOS locations of pinnipeds at-sea estimated using Fastloc GPS. PLoS ONE 5(1).

GeoOceans (2012). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, October 2012. Technical Report. Prepared for Cardno on behalf of INPEX.

GeoOceans (2013a). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, November 2013. Technical Report. Prepared for Cardno on behalf of INPEX.

Geo Oceans (2013b). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, July 2013. Technical Report. Prepared for Cardno on behalf of INPEX, July 2013.

GeoOceans (2014). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, October 2014. Technical Report. Prepared for Cardno on behalf of INPEX.

Hodgson, A., Marsh, H., Marsh, L., Grech, A., McMahon, A. and Parra, G. (2011). Dugong Aerial Survey Manual. James Cook University, Townsville.

INPEX (2011). Ichthys Gas Field Development Project- Draft Environmental Impact Statement. INPEX Operations Australia Pty Ltd.

INPEX (2013). Dredging and Spoil Disposal Management Plan – East Arm Rev 4. INPEX Operations Australia Pty Ltd.

INPEX (2014). Dredging and Spoil Disposal Management Plan – Gas Export Pipeline Rev 7. INPEX Operations Australia Pty Ltd.

Lanyon, J. (2007). Determining critical reproductive parameters for a subtropical dugong population. Report to the Australian Centre for Marine Mammal Science, Australian Antarctic Division.



Marsh, H. (1999). Reproduction in sirenians. In: Biology of Marine Mammals. J.E. Reynolds, III and S.A. Rommel, eds. pp. 243-256. Smithsonian Institution Press.

Marsh, H. and Sinclair, D.F. (1989). Correcting for visibility bias in strip transect aerial surveys of aquatic fauna. Journal of Wildlife Management, 53, pp. 1017-1024.

Marsh, H., Penrose, H., Eros, C. and Hughes, J. (2002). Dugong: status reports and action plans for countries and territories in its range. Cambridge, UK: IUCN.

NAILSMA (2006). Dugong and marine turtle knowledge handbook. North Australian Indigenous Land and Sea Management Alliance. Feb 2006. 132 pp.

Pollock, K., Marsh, H., Lawler, I. R. and Alldredge, M.W. (2006). Estimating animal abundance in heterogeneous environments: an application to aerial surveys for dugongs. Journal of Wildlife Management, 70, pp. 255-262.

Preen, A.R. (1992). Interactions between dugongs and seagrasses in a sub-tropical environment. Page(s) 392. Ph.D. Thesis. James Cook University, Townsville.

Whiteway, T. (2009). Australian Bathymetry and Topography Grid. Geoscience Australia.

Whiting, S.D. (2000). ‘The ecology of immature green and hawksbill turtles foraging on two reef systems in northern Australia’, PhD Thesis. Northern Territory University, Darwin.

Whiting, S.D. (2002). Rocky reefs provide foraging habitat for dugongs in the Darwin region of northern Australia. Australian Mammalogy, 24, pp. 147-150.




Ichthys Nearshore Environmental Monitoring Program

APPENDIX A SUMMARY OF AERIAL SURVEY EFFORT DURING BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix A Summary of aerial survey effort for each block (C1, IM and C2) during Baseline (B1, B2 and B3), Dredging (D2, D3, D4 and D5) and Post-dredging (P1 and P2) Phase surveys

Survey Period Number of transects Total length transectsª (km)

Total sampled area (km²)

Overall surveyed area (km²)

Proportion surveyed* (%)

Average survey duration

(h: min: sec)

Bynoe Harbour

(C1)

B1 20 299.50 119.80 598.08 20.03 0:54:17 B2 20 350.30 140.12 693.45 20.21 1:23:23 B3 20 349.88 139.95 688.17 20.34 1:27:53 D2 20 349.88 139.95 688.17 20.34 1:06:32 D3 20 – 22^ 348.37 – 344.94^ 139.35 – 137.98^ 687.03 20.28 – 20.08^ 1:58:20 D4 20 348.37 139.35 687.03 20.28 1:50:29 D5 20 348.37 139.35 687.03 20.28 1:45:55 P1 17** – 20 274.35** – 348.37 109.74** – 139.35 569.62** – 687.03 19.27** – 20.28 1:45:32 P2 20 348.37 139.35 687.03 20.28 1:42:44

Darwin Harbour

(IM)

B1 29 524.40 209.76 1029.43 20.38 1:25:47 B2 27 517.40 206.96 1024.05 20.21 1:25:36 B3 27 517.72 207.09 1019.58 20.31 1:26:55 D2 27 517.72 207.09 1019.58 20.31 1:36:53 D3 27 519.26 207.70 1034.49 20.08 2:47:28 D4 27 518.01 207.21 1034.49 20.03 2:43:22 D5 27 518.01 207.21 1034.49 20.03 2:43:10 P1 27 518.01 207.21 1034.49 20.03 2:44:56 P2 27 518.01 207.21 1034.49 20.03 2:33:43

Vernon Islands

(C2)

B1 21 469.60 187.84 929.35 20.21 1:36:17 B2 22 491.90 196.76 971.84 20.25 1:12:08 B3 22 492.04 196.82 969.83 20.29 1:20:36 D2 22 492.04 196.82 969.83 20.29 1:15:09 D3 19^ – 22 482.85^ – 492.01 193.14^ – 196. 80 975.91 19.79^ – 20.17 2:28:04 D4 22 492.01 196.80 975.91 20.17 2:24:33 D5 19 482.85 193.14 975.91 19.79 2:24:25 P1 19^ – 22 482.85^ – 492.01 193.14^ – 196. 80 975.91 19.79^ – 20.17 2:28:37 P2 22 492.01 196.80 975.91 20.17 2:19:41

ª Transect length over water. * The proportion of surveyed area is averaged in the calculation of total area surveyed. ^ Variation due to flight orientation. ** Variation due to error with aircraft flight plan. As a result, transects 78 to 82 of the alternate orientation were unable to be flown.


Prepared for INPEX Cardno


APPENDIX B SUMMARY OF DUGONG SIGHTINGS ACROSS BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix B Summary of the number of dugongs recorded during Baseline (B1, B2 and B3), Dredging (D2, D3, D4 and D5) and Post-dredging (P1 and P2) Phase surveys All areas All areas Total sightings

Survey period P1 P2 B1 B2 B3 D2 D3 D4 D5

Replication number R1 R2 R3 Total R1 R2 R3 Total

Number of observations 24 17 21 62 13 14 27 54 45 62 81 28 52 64 75

Number of animals 32 28 25 85 19 20 38 77 58 92 113 33 71 87 97

Number of calves 4 2 2 8 3 5 0 8 4 7 2 1 4 7 3

Maximum group size 3 5 3 5 3 2 3 3 3 4 7 3 4 4 4

Bynoe Harbour (C1) Bynoe Harbour (C1) Total sightings


Replication number R1* R2 R3 Total R1 R2 R3 Total



Number of calves 0 0 0 0 1 0 0 1 1 0 0 0 1 0 1


Darwin Harbour (IM) Darwin Harbour (IM) Total sightings


Replication number R1* R2 R3* Total R1 R2 R3 Total



Number of calves 0 0 0 0 1 3 0 4 2 5 2 1 1 5 0


Vernon Islands (C2) Vernon Islands (C2) Total sightings





Number of calves 4 2 2 8 1 2 0 3 1 2 0 0 2 2 2

Maximum group size 3 5 3 5 3 2 1 3 3 4 2 3 2 4 4 B1 = 2 replicates; B2, B3, D3, D4, P1, P2 = 3 replicates; and D2 and D5 = 2 replicates of C2, 3 replicates of C1 and IM.




APPENDIX C SUMMARY OF DUGONG AND TURTLE SIGHTINGS OVERLAID WITH CONFIRMED SEAGRASS HABITAT DURING B3, D4 AND P2 SURVEYS



Appendix C-1 Distribution of dugongs in Darwin Harbour and surrounding areas in October 2012 (B3), October 2013 (D4) and October 2014 (P2), overlaid with mapped seagrass habitat (seagrass data for October 2012, November 2013 and October 2014, respectively; Geo Oceans 2012, 2013a, 2014)



Appendix C-2 Distribution of turtles in Darwin Harbour and surrounding areas in October 2012 (B3), October 2013 (D4) and October 2014 (P2), overlaid with mapped seagrass habitat (seagrass data for October 2012, November 2013 and October 2014, respectively; Geo Oceans 2012, 2013a, 2014)




APPENDIX D DUGONG POPULATION SIZE ESTIMATES DURING BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix D Comparison of dugong population size estimates (±SE) during the Baseline Phase (B1, B2 and B3), Dredging Phase (D2, D3, D4 and D5) and Post-dredging Phase (P2)

Marsh and Sinclair (1989) Pollock et al. (2006) Block Month Replicate Estimate ± SE Estimate ± SE

C1

June (B1)

1 238 86 121 87

2 114 40 100 83

3 - - - -

July (B2) 1 - - - - 2 - - - - 3 287 65 424 206

October (B3)

1 81 74 68 35

2 232 149 122 51

3 - - - -

May (D2)

1 - - - -

2 - - - -

3 - - - -

July (D3)

1 - - - -

2 134 58 41 11

3 - - - -

October (D4)

1 - - - -

2 - - - -

3 181 84 62 27

May (D5)

1 187 63 138 34

2 158 56 131 29

3 - - - -

October (P2)

1 - - - -

2 - - - -

3 123 59 61 20

C2

June (B1)

1 252 85 130 71

2 124 45 98 79

3 - - - -

July (B2)

1 - - - -

2 - - - -

3 325 78 273 139

October (B3)

1 99 42 76 30

2 337 103 162 42

3 - - - -

May (D2)

1 - - - -

2 93 45 67 26

3 - - - -

July (D3)

1 - - - -

2 - - - -

3 - - - -




October (D4)

1 192 106 126 52

2 327 148 171 76

3 - - - -

May (D5)

1 187 105 159 62

2 455 208 389 141

3 - - - -

October (P2)

1 129 96 98 59 2 149 75 106 41 3 - - - -

IM

June (B1)

1 254 76 128 67

2 232 56 185 121

3 - - - -

July (B2)

1 461 138 223 111

2 361 139 274 180

3 - - - -

October (B2)

1 485 161 434 82

2 364 185 180 56

3 353 207 190 69

May (D2)

1 - - - -

2 - - - -

3 99 48 90 37

July (D3)

1 329 208 176 66

2 225 113 126 50

3 390 246 151 57

October (D4)

1 281 141 164 55

2 446 147 226 66

3 418 212 189 58

May (D5)

1 349 103 313 79

2 - - - -

3 210 76 182 62

October (P2)

1 180 116 86 29 2 180 96 123 48 3 559 299 351 131

N.B. No population estimates were not derived for P1 (July 2014) due to poor survey conditions, refer to Section 4.1.1.




APPENDIX E CORRECTED DUGONG DENSITIES DURING BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix E Dugong density (±SE) for blocks C1, C2 and IM during the Baseline Phase (B1, B2 and B3), Dredging Phase (D2, D3, D4, and D5) and Post-dredging Phase (P2), using the Marsh and Sinclair (1989) and the Pollock et al. (2006) methods and raw sightings data

Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE

C1

June (B1)

1 0.30 0.11 0.15 0.11 0.07

2 0.14 0.05 0.13 0.10 0.05

3 - - - - -

July (B2)

1 - - - - 0.01

2 - - - - 0.02

3 0.34 0.08 0.50 0.24 0.11

October (B3)

1 0.10 0.09 0.08 0.04 0.04

2 0.29 0.18 0.15 0.06 0.06

3 - - - - 0.05

May (D2)

1 - - - - 0.01

2 - - - - 0.01

3 - - - - 0.01

July (D3)

1 - - - - 0.06

2 0.20 0.08 0.06 0.02 0.05

3 - - - - 0.03

October (D4)

1 - - - - 0.01

2 - - - - 0.04

3 0.26 0.12 0.09 0.04 0.04

May (D5)

1 0.27 0.09 0.20 0.05 0.06

2 0.23 0.08 0.19 0.04 0.06

3 - - - - 0.01

October (P2)

1 - - - - 0.01 2 - - - - 0.01 3 0.18 0.09 0.09 0.03 0.05

C2

June (B1)

1 0.25 0.08 0.13 0.07 0.06

2 0.12 0.04 0.10 0.08 0.04

3 - - - - -

July (B2)

1 - - - - 0.02

2 - - - - 0.02

3 0.32 0.08 0.27 0.14 0.11

October (B3)

1 0.10 0.04 0.07 0.03 0.04

2 0.33 0.10 0.16 0.04 0.09

3 - - - - 0.02

May (D2)

1 - - - - 0.02

2 0.09 0.04 0.07 0.03 0.04

3 - - - - -

July (D3)

1 - - - - 0.03

2 - - - - 0.02

3 - - - - 0.02



Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE

October (D4)

1 0.20 0.11 0.13 0.05 0.06

2 0.34 0.15 0.18 0.08 0.08

3 - - - - 0.01

May (D5)

1 0.19 0.11 0.16 0.06 0.06

2 0.47 0.21 0.40 0.14 0.14

3 - - - - -

October (P2)

1 0.13 0.10 0.10 0.06 0.04 2 0.15 0.08 0.11 0.04 0.05 3 - - - - 0.01

IM

June (B1)

1 0.21 0.06 0.11 0.06 0.05

2 0.19 0.05 0.15 0.10 0.07

3 - - - - -

July (B2)

1 0.40 0.12 0.19 0.10 0.10

2 0.31 0.12 0.24 0.15 0.08

3 - - - - 0.03

October (B3)

1 0.43 0.14 0.38 0.07 0.17

2 0.32 0.16 0.16 0.05 0.08

3 0.31 0.18 0.17 0.06 0.07

May (D2)

1 - - - - 0.01

2 - - - - 0.02

3 0.09 0.04 0.08 0.03 0.04

July (D3)

1 0.32 0.20 0.17 0.06 0.08

2 0.22 0.11 0.12 0.05 0.05

3 0.38 0.24 0.15 0.06 0.06

October (D4)

1 0.27 0.14 0.16 0.05 0.07

2 0.43 0.14 0.22 0.06 0.09

3 0.40 0.20 0.18 0.06 0.07

May (D5)

1 0.34 0.10 0.30 0.08 0.10

2 - - - - 0.02

3 0.20 0.07 0.18 0.06 0.06

October (P2)

1 0.17 0.11 0.08 0.03 0.04 2 0.17 0.09 0.04 0.12 0.05 3 0.54 0.29 0.34 0.13 0.14




APPENDIX F SUMMARY OF TURTLE SIGHTINGS ACROSS BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix F Summary of the number of turtles recorded during Baseline (B1, B2 and B3), Dredging (D2, D3, D4 and D5) and Post-dredging (P1 and P2) Phase

All Areas All Areas Total sightings






Bynoe Harbour (C1) Bynoe Harbour (C1) Total sightings


Replication number R1 R2 R3 Total R1 R2 R3 Total Total




Darwin Harbour (IM) Darwin Harbour (IM) Total sightings






Vernon Islands (C2) Vernon Islands (C2) Total sightings






B1 = 2 replicates; B2, B3, D3, D4, P1, P2 = 3 replicates; and D2 and D5 = 2 replicates of C2, 3 replicates of C1 and IM.




APPENDIX G TURTLE POPULATION SIZE ESTIMATES DURING BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix G Comparison of turtle population size estimates (±SE) during the Baseline Phase (B1, B2, and B3), Dredging Phase (D2, D3, D4, and D5) and Post-dredging Phase (P2)


Block Month Replicate Estimate ± SE Estimate ± SE

C1

June (B1)

1 372 47 399 256

2 297 46 301 197

3 - - - -

July (B2)

1 2,291 332 2,302 822

2 427 90 428 261

3 1,280 132 1,260 632

October (B3)

1 877 161 864 154

2 755 179 744 148

3 703 182 690 203

May (D2)

1 517 106 492 140

2 941 144 922 180

3 918 149 931 196

July (D3)

1 653 153 542 152

2 659 162 566 157

3 642 123 542 99

October (D4)

1 834 117 703 156

2 373 71 320 92

3 478 114 387 114

May (D5)

1 705 91 743 128

2 838 132 875 168

3 567 97 689 158

October (P2)

1 370 76 698 162

2 621 106 1,514 257

3 888 146 1,647 203

C2

June (B1)

1 1,001 151 1,113 714

2 579 92 551 333

3 - - - -

July (B2)

1 1,380 292 1,427 552

2 693 89 695 394

3 587 68 728 427

October (B3)

1 877 116 878 136

2 1,059 97 1,067 125

3 472 91 481 149

May (D2)

1 488 95 559 133

2 763 153 881 147

3 - - - -

July (D3)

1 374 88 364 60

2 555 116 540 94

3 766 134 720 137




October (D4)

1 685 88 669 115

2 773 117 735 184

3 1,017 175 943 199

May (D5)

1 864 103 928 166

2 1,162 131 1,131 203

3 - - - -

October (P2)

1 560 89 950 110

2 868 129 1,482 196

3 625 80 1,273 143

IM

June (B1)

1 698 250 740 475

2 780 92 764 479

3 - - - -

July (B2)

1 2,711 607 2,770 1044

2 957 149 965 547

3 740 138 576 238

October (B3)

1 1,428 143 1,420 192

2 513 113 489 105

3 662 112 652 178

May (D2)

1 287 54 315 68

2 391 69 425 98

3 557 89 559 132

July (D3)

1 664 156 613 98

2 642 157 572 90

3 609 152 555 87

October (D4)

1 683 102 625 114

2 539 84 484 87

3 710 101 650 130

May (D5)

1 714 103 695 139

2 290 62 291 50

3 369 53 454 90

October (P2)

1 454 93 804 154

2 539 91 1,191 142

3 989 113 2,001 224 N.B. No population estimates were not derived for P1 (July 2014) due to poor survey conditions, refer to Section 4.1.1.




APPENDIX H CORRECTED TURTLE DENSITIES DURING BASELINE, DREDGING AND POST-DREDGING PHASE SURVEYS



Appendix H Turtle density (±SE) for blocks C1, C2 and IM during the Baseline Phase (B1, B2 and B3), Dredging Phase (D2, D3, D4 and D5) and Post-dredging Phase (P2), using the Marsh and Sinclair (1989) and the Pollock et al. (2006) methods and raw sightings data

Marsh and Sinclair (1989) Pollock et al. (2006) Raw


C1

June (B1)

1 0.47 0.06 0.50 0.32 0.23

2 0.37 0.06 0.38 0.25 0.21

3 - - - - -

July (B2)

1 2.70 0.39 2.71 0.97 0.38

2 0.50 0.11 0.50 0.31 0.23

3 1.51 0.16 1.48 0.74 0.73

October (B3)

1 1.08 0.20 1.06 0.19 0.72

2 0.93 0.22 0.92 0.18 0.73

3 0.87 0.22 0.85 0.25 0.57

May (D2)

1 0.75 0.15 0.61 0.17 0.40

2 1.37 0.21 1.14 0.22 0.78

3 1.33 0.22 1.15 0.24 0.77

July (D3)

1 0.95 0.22 0.79 0.22 0.42

2 0.96 0.24 0.82 0.23 0.42

3 0.93 0.18 0.79 0.14 0.41

October (D4)

1 1.21 0.17 1.02 0.23 0.67

2 0.54 0.10 0.47 0.13 0.31

3 0.70 0.17 0.56 0.17 0.38

May (D5)

1 1.03 0.13 1.08 0.19 0.78

2 1.22 0.19 1.27 0.24 0.92

3 0.83 0.14 1.00 0.23 0.70

October (P2)

1 0.54 0.11 1.02 0.24 0.42 2 0.90 0.15 2.20 0.37 0.80 3 1.29 0.21 2.40 0.30 1.08

C2

June (B1)

1 0.98 0.15 1.09 0.70 0.47

2 0.56 0.09 0.54 0.32 0.33

3 - - - - -

July (B2)

1 1.35 0.28 1.39 0.54 0.26

2 0.68 0.09 0.68 0.38 0.32

3 0.57 0.07 0.71 0.42 0.40

October (B3)

1 0.86 0.11 0.86 0.13 0.60

2 1.04 0.10 1.05 0.12 0.85

3 0.46 0.09 0.47 0.15 0.34

May (D2)

1 0.48 0.09 0.55 0.13 0.31

2 0.75 0.15 0.86 0.14 0.53

3 - - - - -

July (D3)

1 0.38 0.09 0.37 0.06 0.23

2 0.57 0.12 0.55 0.10 0.32

3 0.78 0.14 0.74 0.14 0.44



Marsh and Sinclair (1989) Pollock et al. (2006) Raw


October (D4)

1 0.70 0.09 0.69 0.12 0.54

2 0.79 0.12 0.75 0.19 0.59

3 1.04 0.18 0.97 0.20 0.77

May (D5)

1 0.89 0.11 0.95 0.17 0.70

2 1.19 0.13 1.16 0.21 0.85

3 - - - - -

October (P2)

1 0.57 0.09 0.97 0.11 0.48 2 0.89 0.13 1.52 0.20 0.71 3 0.64 0.08 1.30 0.15 0.54

IM

June (B1)

1 0.58 0.21 0.61 0.39 0.27

2 0.64 0.08 0.63 0.40 0.36

3 - - - - -

July (B2)

1 2.33 0.52 2.38 0.90 0.36

2 0.82 0.13 0.83 0.47 0.39

3 0.64 0.12 0.49 0.20 0.25

October (B3)

1 1.25 0.13 1.25 0.17 0.88

2 0.45 0.10 0.43 0.09 0.39

3 0.58 0.10 0.57 0.16 0.42

May (D2)

1 0.25 0.05 0.28 0.06 0.21

2 0.34 0.06 0.37 0.09 0.30

3 0.49 0.08 0.49 0.12 0.40

July (D3)

1 0.64 0.15 0.59 0.09 0.24

2 0.62 0.15 0.55 0.09 0.26

3 0.59 0.15 0.54 0.08 0.27

October (D4)

1 0.66 0.10 0.60 0.11 0.43

2 0.52 0.08 0.47 0.08 0.33

3 0.69 0.10 0.63 0.13 0.44

May (D5)

1 0.69 0.10 0.67 0.13 0.47

2 0.28 0.06 0.28 0.05 0.20

3 0.36 0.05 0.44 0.09 0.26

October (P2)

1 0.44 0.09 0.78 0.15 0.36 2 0.52 0.09 1.15 0.14 0.44 3 0.96 0.11 1.93 0.22 0.78




APPENDIX I TURTLE SUB-BLOCK POPULATION SIZE ESTIMATES DURING P2 AERIAL SURVEYS



Appendix I Turtle sub-block population size estimates (±SE) in C1, IM and C2 during P2 (October 2014)

Block Sub-block Replicate Sightings in Transect Marsh and Sinclair (1989) Pollock et al. (2006)

Estimate ±SE Estimate ±SE

C1

1

1 3 14 6 40 16

2 7 37 11 93 37

3 6 37 20 69 24

Average 5 29 14 68 33

2

1 38 231 65 519 146

2 71 361 86 900 252

3 89 552 140 1077 245

Average 66 381 130 846 263

3

1 17 108 40 236 91

2 27 161 48 377 111

3 36 186 39 454 121

Average 27 152 48 356 120

4

1 0 - - - -

2 6 35 16 87 31

3 20 131 49 247 79

Average 9 83 49 167 82

IM

1

1 10 51 20 127 55

2 17 107 30 231 69

3 49 290 37 627 125

Average 25 149 81 328 176

2

1 14 80 32 149 57

2 14 95 22 190 61

3 21 134 35 274 74

Average 16 103 31 204 68

3

1 16 105 40 177 53

2 22 135 38 273 89

3 30 196 61 379 118

Average 23 145 48 276 98

4

1 26 160 29 337 84

2 22 139 16 281 70

3 30 150 25 277 72

Average 26 150 23 298 72

5

1 6 35 14 76 22

2 13 79 30 163 63

3 25 149 20 271 64

Average 15 88 42 170 78



Block Sub-block Replicate Sightings in Transect Marsh and Sinclair (1989) Pollock et al. (2006)


6

1 2 10 5 26 6

2 4 19 4 52 19

3 9 53 12 116 42

Average 5 28 15 64 34

C2

1

1 17 99 38 217 83

2 27 153 65 302 118

3 20 118 32 244 63

Average 21 123 50 254 93

2

1 42 262 68 336 79

2 59 321 79 604 142

3 53 306 59 583 95

Average 51 296 68 508 153

3

1 25 134 23 321 79

2 38 219 44 393 82

3 22 124 26 283 72

Average 28 159 49 333 80

4

1 10 65 6 130 39

2 15 90 33 180 68

3 11 70 16 130 31

Average 12 75 23 147 51




APPENDIX J CORRECTED TURTLE SUB-BLOCK DENSITIES DURING P2 AERIAL SURVEYS



Appendix J Turtle sub-block corrected densities within C1, IM and C2 during P2 (October 2014)

Block Sub-Block Replicate Area

(km2) Sightings in

Transect Marsh and Sinclair

(1989) Pollock et al. (2006)


C1

1

1

94.7

3 0.15 0.06 0.42 0.17

2 7 0.39 0.12 0.99 0.39

3 6 0.39 0.21 0.73 0.25

2

1

296.4

38 0.78 0.22 1.75 0.49

2 71 1.22 0.29 3.04 0.85

3 89 1.86 0.47 3.63 0.83

3

1

150.2

17 0.72 0.27 1.57 0.61

2 27 1.07 0.32 2.51 0.74

3 36 1.24 0.26 3.02 0.81

4

1

145.8

0 - - - - 2 6 0.24 0.11 0.60 0.21

3 20 0.90 0.34 1.69 0.54

IM

1

1

193.8

10 0.26 0.10 0.66 0.29

2 17 0.55 0.16 1.19 0.36

3 49 1.50 0.19 3.23 0.64

2

1

128.7

14 0.62 0.25 1.16 0.44

2 14 0.73 0.17 1.48 0.48

3 21 1.04 0.27 2.13 0.57

3

1

121.5

16 0.87 0.33 1.45 0.43

2 22 1.11 0.31 2.25 0.73

3 30 1.61 0.51 3.12 0.97

4

1

171.5

26 0.93 0.17 1.96 0.49

2 22 0.81 0.10 1.64 0.41

3 30 0.87 0.15 1.61 0.42

5

1

85.9

6 0.40 0.16 0.89 0.25

2 13 0.92 0.35 1.90 0.73

3 25 1.73 0.23 3.16 0.75

6

1

333.1

2 0 0 0 0 2 4 0.06 0.01 0.16 0.06

3 9 0.16 0.04 0.35 0.13

C2

1

1

224.5

17 0.44 0.17 0.97 0.37

2 27 0.68 0.29 1.35 0.52

3 20 0.53 0.14 1.09 0.28

2

1

207.1

42 1.26 0.33 1.62 0.38

2 59 1.55 0.38 2.92 0.69

3 53 1.48 0.29 2.81 0.46

3

1

393.6

25 0.34 0.06 0.82 0.20

2 38 0.56 0.11 1.00 0.21

3 22 0.32 0.07 0.72 0.18



Block Sub-Block Replicate Area

(km2) Sightings in

Transect Marsh and Sinclair

(1989) Pollock et al. (2006)


4

1

150.7

10 0.43 0.04 0.86 0.26

2 15 0.60 0.22 1.20 0.45

3 11 0.47 0.11 0.86 0.21




APPENDIX K LAND SURVEY DATA DURING P2 SURVEY



Appendix K Land-based observations of individuals at Channel Island and Cullen Bay during P2 survey in October 2014

Location Replicate Date Observer Positions (lat.)

Observer Positions (long.)

Direction observed Time Animal type No. of Individuals Age Class

Bearing from Observer (degrees)

Est. Distance from Observer

Cullen Bay Rep 1 14-Oct-14 12°26.849'S 130°49.404'E W 8:08:00 Dugong 1 Adult 287 150 Cullen Bay Rep 1 14-Oct-14 12°26.849'S 130°49.404'E W 9:24:00 Dugong 1 Adult 307 70 Cullen Bay Rep 1 14-Oct-14 12°26.849'S 130°49.404'E NE 9:31:00 Unidentified Dolphin 1 Adult 45 150 Cullen Bay Rep 1 14-Oct-14 12°26.849'S 130°49.404'E NE 11:14:00 Dugong 1 Adult 78 60 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:07:00 Unidentified Turtle 1 Juvenile 150 180 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:29:00 Green Turtle 1 Juvenile 237 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:30:00 Green Turtle 1 Juvenile 180 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:32:00 Green Turtle 1 Juvenile 126 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:34:00 Green Turtle 1 Adult 185 45 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:39:00 Green Turtle 1 Juvenile 122 75 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:40:00 Green Turtle 1 Adult 165 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:43:00 Unidentified Turtle 1 Juvenile 242 80 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 8:47:00 Green Turtle 1 Juvenile 112 60 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:11:00 Green Turtle 1 Unknown 113 60 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:14:00 Green Turtle 1 Juvenile 195 35 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:19:00 Green Turtle 1 Juvenile 126 80 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:30:00 Green Turtle 1 Juvenile 239 65 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:36:00 Green Turtle 1 Juvenile 139 80 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:57:00 Green Turtle 1 Juvenile 220 45 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 9:58:00 Green Turtle 1 Juvenile 110 80 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 10:05:00 Green Turtle 1 Juvenile 176 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 10:30:00 Green Turtle 1 Juvenile 256 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S -- Green Turtle 1 Juvenile 123 60 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:07:00 Green Turtle 1 Juvenile 193 60 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:07:00 Green Turtle 1 Juvenile 176 110 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:10:00 Green Turtle 1 Juvenile 192 65 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:11:00 Green Turtle 1 Juvenile 189 25 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:17:00 Green Turtle 1 Juvenile 255 65 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:17:00 Green Turtle 1 Juvenile 198 10 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:21:00 Green Turtle 1 Juvenile 181 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E S 11:38:00 Green Turtle 1 Juvenile 242 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 7:46:00 Green Turtle 1 Juvenile 37 25 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 7:50:00 Green Turtle 1 Juvenile 40 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 7:57:00 Green Turtle 1 Juvenile 36 15 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 7:59:00 Green Turtle 1 Juvenile 0 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:04:00 Green Turtle 1 Juvenile 35 70 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:04:00 Green Turtle 1 Juvenile 30 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:05:00 Green Turtle 1 Juvenile 35 35 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:07:00 Green Turtle 1 Juvenile 5 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:09:00 Green Turtle 1 Juvenile 55 10 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:31:00 Green Turtle 1 Juvenile 280 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:38:00 Green Turtle 1 Juvenile 310 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:45:00 Green Turtle 1 Juvenile 70 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:47:00 Green Turtle 1 Juvenile 80 100








Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:50:00 Green Turtle 1 Juvenile 60 25 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 8:52:00 Green Turtle 1 Juvenile 350 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:15:00 Green Turtle 1 Juvenile 85 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:19:00 Green Turtle 1 Juvenile 30 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:33:00 Green Turtle 1 Juvenile 60 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:35:00 Green Turtle 1 Juvenile 280 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:36:00 Green Turtle 1 Juvenile 30 120 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:50:00 Green Turtle 1 Sub-adult 30 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:53:00 Green Turtle 1 Juvenile 60 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:54:00 Green Turtle 1 Juvenile 300 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 9:59:00 Green Turtle 1 Juvenile 60 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:00:00 Green Turtle 1 Juvenile 60 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:06:00 Green Turtle 1 Juvenile 0 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:07:00 Green Turtle 1 Juvenile 280 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:08:00 Green Turtle 1 Juvenile 270 25 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:12:00 Green Turtle 1 Juvenile 330 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:25:00 Green Turtle 1 Juvenile 0 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:28:00 Green Turtle 1 Juvenile 350 120 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:31:00 Green Turtle 1 Juvenile 330 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:35:00 Green Turtle 1 Juvenile 70 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:40:00 Green Turtle 1 Juvenile 280 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:40:00 Green Turtle 1 Juvenile 330 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 10:48:00 Green Turtle 1 Juvenile 330 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:03:00 Green Turtle 1 Juvenile 340 100 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:04:00 Green Turtle 1 Juvenile 350 70 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:10:00 Green Turtle 1 Juvenile 30 10 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:19:00 Green Turtle 1 Juvenile 40 50 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:22:00 Green Turtle 1 Juvenile 40 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:26:00 Green Turtle 1 Juvenile 90 10 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:38:00 Green Turtle 1 Juvenile 90 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:44:00 Green Turtle 1 Juvenile 45 40 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 11:57:00 Green Turtle 1 Juvenile 320 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 12:00:00 Green Turtle 1 Juvenile 30 20 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 12:11:00 Green Turtle 1 Juvenile 20 30 Channel Island Rep 1 14-Oct-14 12°33.242'S 130°52.419'E N 12:17:00 Green Turtle 1 Juvenile 280 50 Cullen Bay Rep 2 23-Oct-14 12°26.849'S 130°49.404'E NE 11:18:00 Snubfin Dolphin 1 Adult 325 65 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 8:17:00 Unidentified Turtle 1 Juvenile 40 150 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 8:25:00 Unidentified Turtle 1 Juvenile 356 50 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 8:33:00 Green Turtle 1 Juvenile 10 20 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 8:37:00 Green Turtle 1 Juvenile 325 20 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 8:38:00 Green Turtle 1 Juvenile 340 40 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:03:00 Green Turtle 1 Juvenile 355 30 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:03:00 Green Turtle 1 Juvenile 360 40 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:16:00 Unidentified Turtle 1 Unknown 68 60 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:24:00 Green Turtle 1 Juvenile 49 50








Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:25:00 Green Turtle 1 Juvenile 18 60 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 9:29:00 Unidentified Turtle 1 Unknown 40 60 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 10:51:00 Unidentified Turtle 1 Juvenile 318 110 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 10:52:00 Unidentified Turtle 1 Juvenile 337 100 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E N 11:07:00 Green Turtle 1 Sub-adult 330 50 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:00:00 Unidentified Turtle 2 Adult 166 70 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:12:00 Unidentified Turtle 1 Adult 169 60 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:13:00 Green Turtle 1 Adult 153 20 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:14:00 Unidentified Turtle 1 Adult 155 50 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:31:00 Green Turtle 1 Juvenile 251 10 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 8:54:00 Unidentified Turtle 1 Juvenile 255 40 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 9:28:00 Green Turtle 2 Juvenile 170 15 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 9:45:00 Green Turtle 1 Juvenile 185 35 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 9:59:00 Green Turtle 1 Juvenile 168 40 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:14:00 Unidentified Turtle 1 Juvenile 165 70 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:17:00 Green Turtle 1 Juvenile 150 75 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:28:00 Unidentified Turtle 1 Juvenile 230 120 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:47:00 Green Turtle 2 Juvenile 145 65 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:49:00 Green Turtle 1 Adult 145 65 Channel Island Rep 2 23-Oct-14 12°33.242'S 130°52.419'E S 10:54:00 Green Turtle 1 Adult 168 50




APPENDIX L REHABILITATED TURTLE SUMMARY DATA



Appendix L Details of turtle rehabilitation as of November 2014 ID No.

Date of Stranding

Turtle Species and Life Stage

General location of Stranding Injuries Rehab details Release details Comments

Approximate rehab time (months)

Proposed release location Suitability for tagging Release details Release date

1 July 2011 Olive Ridley (juvenile) Bare Sand Island

Hatchling severely dehydrated and weakened. Taken to Territory Wildlife Park for recovery

22 months Bynoe Harbour- Bare Sand Island

Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Timor Research Facility, NAMRA, May 2013

May 2013 "Oliver" – as of Sept 2013, tracks still being transmitted, data on Seaturtle.org

2 July 2011 Flatback (juvenile) Bare Sand Island

Hatchling severely dehydrated and weakened. Taken to Territory Wildlife Park for recovery

22 months Bynoe Harbour- Bare Sand Island

Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Research Station, CDU, May 2013

May 2013 "Henderson" – as of Sept 2013, tracks still being transmitted, data on Seaturtle.org

3 September 2012

Flatback (adult) Darwin Harbour Boat strike injury – mid

carapace damage 6 months NA

Unsuitable for TDMP due to boat strike injury (position needed for harness and transmitter) – flipper tagged attached by Kiki

Released – Ray Chatto (DLRM) February 2013

Turtle measurements: 56.8cm long, 48.9cm wide & weighs 20kg; the plastron length is 55.5 cm & width is 54.8cm. Boat strike injury left a significant area of scar tissue on the turtle’s carapace. The turtle was not able to carry a harness due to the injury. Released without satellite tag, flipper tagged by Ray Chatto on release in February 2013

4 October 2012

Flatback (adult female)

East of Hotham Point (~70 km from Darwin)

Floater 1 month Lee Point Unsuitable for TDMP, but released by Kiki

Released - Kiki Dethmers, Arafura Timor Research Facility, NAMRA, - satellite transmitter attached & flipper tagged at Lee Point

7 December 2012

Turtle measured on captured by TD team in early Oct 2012, 81.9cm long (CCL), 67cm wide (CCW), weight 67kg; "Michala" – tracks transmitted for 2 months, data on Seaturtle.org

5 October 2012

Flatback (juvenile)

Pioneer Beach, Bynoe Harbour Floater (no other injuries) NA NA nil NA NA Unknown

6 unknown Green (unknown)

Found at Mandorah Beach, Darwin Harbour

Boat strike injury – severe head and carapace damage

unknown unknown unknown Unknown Unknown Unknown

7 May 2013 Flatback (adult male) Near Charles Point Possible boat strike,

carapace damage 1.5 months Nightcliff jetty Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Timor Research Facility, NAMRA, May 2013

May 2013 "Charlie" – as of Sept 2013, trackes still being transmitted, data on Seaturtle.org

8 May 2013 Hawksbill (juvenile) Darwin Harbour Head injury 3 to 4 months To be determined

Unsuitable for TDMP-the turtle was found outside of the project area

will be released in late 2013, not suitable for TDMP

August/September 2013

Still in rehab (as of Sept 2013), update from Stephen Cutter (21 Aug) - head injuires appear to have subsided- the turtle will be flipper tagged and released

9 May 2013 Hawksbill (juvenile) Darwin Harbour Darwin Harbour Unsuitable- missing fore flipper Released without tag by

Ray Chatto, May 2013 May 2013

10 July 2013 Flatback (juvenile) Darwin Harbour Floater? Boat strike unknown unknown Unsuitable for TDMP – targeted species include Hawksbill and Green Turtles

will be released in late 2013, not suitable for TDMP

TBC Housed at CDU - update from SC (21 Aug) – will be released late 2013 and tagged by Kiki Dethmers

11 October 2013

Green (unknown) Bynoe Harbour 46 kg Floater, very

dehydrated, very sunken died overnight nil nil (past away) NA NA NPWS picked up turtle 30/10

12 March 2014 Green (male adult?) Casuarina Beach

Prop wound to the rear right quarter of his shell, partially penetrating intramuscular and a severe gash diagonally down the upper side of his tail

86 kg unknown, but good chance of recovery

Casuarina Beach unknown at this stage Unknown

Marine Wildwatch Id Number = 2014_453 Danny Low Choy (Marine Wildwatch Officer)



ID No.

Date of Stranding

Turtle Species and Life Stage

General location of Stranding Injuries Rehab details Release details Comments

Approximate rehab time (months)

Proposed release location Suitability for tagging Release details Release date

13 March 2014 Hawksbill (adult female – Linh)

Evans Shoal (250 km north of Darwin)

No severe injuries except for shallow puncture wound (potentially from a spear) on top right hand side of the carapace.

10 days rehabilitation Nightcliff Jetty

Satellite and flipper tagged. Not included as part of TDMP as it was located outside of project area.

Released with satellite tag by Rachel Groom from DLRM from Nightcliff Jetty, Darwin.

27 March 2014

After much discussion, it was decided 'Linh' should be released locally at Nightcliff Jetty instead of travelling 36 hours to the initial point of capture 250 km north of Darwin between Evans Shoal and Kupang. The satellite tag successfully transmitted data up to August 2014.

18 August 2014 Flatback Turtle (adult)

Casuarina Beach, Lee Point No obvious injuries NA NA NA

Flipper tagged and released: L:QA19198 R:QA19199

12 August 2014

Mature female, no nest evident, tracks indicate the animal travelled up the sand dune, through the burnt fringing vegetation and onto the grass close to the car park. Following tagging by rangers, turtle attempted to return to the water. Animal in good health although appeared exhausted, no damage, clean carapace and no barnacles.

19 September 2014

Hawksbill (unknown) Bynoe Harbour

Floater but alive, heavily encrusted with barnacles and algae

Unknown Unknown NA Unknown Unknown

Recovered from mouth of Annie River, Bynoe Harbour and taken to Animal Ark Hospital for treatment. Condition poor (3kg), weak, heavily encrusted with barnacles (top and bottom) and algae. Treated with antibiotics, fluids, guarded prognosis.

22 October 2014

Flatback Turtle (hatchling) Palmerston Alive, no obvious injuries Unknown Unknown NA Unknown Unknown

2 hatchlings about the same size, seized from housing commission in Palmerston. Measurements same for both, CCL 6 cm, CCW 5 cm, head width 15 mm

23 November 2014

Olive Ridley (unknown) WA Border

Floater, alive but died overnight. In poor condition

Died overnight NA NA NA NA

Floating male turtle, picked up by fishing boat from WA border. Brought to Animal Ark but died over weekend. Brought to Berrimah vet lab for autopsy. Turtle measurements, 58 cm straight carapace length, CCL 60 cm, body weight 18 kg, tail extended 5 mm past carapace. See following.

turtle and dugong monitoring post-dredging report - … · turtle and dugong monitoring...

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